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 $91.76   4.832%   $96.1938   $96.19   $96.20   $96.20  
  Purchase #2 $186.43   4.319%   $194.4819   $194.48   $194.50   $194.50  
  Purchase #3 $16.81   7.433%   $18.0595   $18.06   $18.05   $18.10  
  Purchase #4 $238.86   11.200%   $265.6123   $265.61   $265.60   $265.60  
  Purchase #5 $68.88   8.386%   $74.6563   $74.66   $74.65   $74.70  
  Purchase #6 $246.81   9.508%   $270.2767   $270.28   $270.30   $270.30  
  Purchase #7 $216.26   13.613%   $245.6995   $245.70   $245.70   $245.70  
  7 purchase totals = $1,065.81       $1,164.9800   $1,164.98   $1,165.00   $1,165.10