Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $111.43   12.790%   $125.6819   $125.68   $125.70   $125.70  
  Purchase #2 $241.31   10.336%   $266.2518   $266.25   $266.25   $266.30  
  Purchase #3 $117.77   11.191%   $130.9496   $130.95   $130.95   $130.90  
  Purchase #4 $236.82   11.241%   $263.4409   $263.44   $263.45   $263.40  
  Purchase #5 $126.73   8.657%   $137.701   $137.70   $137.70   $137.70  
  Purchase #6 $235.68   10.518%   $260.4688   $260.47   $260.45   $260.50  
  Purchase #7 $171.35   5.683%   $181.0878   $181.09   $181.10   $181.10  
  7 purchase totals = $1,241.09       $1,365.5818   $1,365.58   $1,365.60   $1,365.60