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 $41.33   7.766%   $44.5397   $44.54   $44.55   $44.50  
  Purchase #2 $188.54   4.220%   $196.4964   $196.50   $196.50   $196.50  
  Purchase #3 $78.45   12.269%   $88.075   $88.08   $88.10   $88.10  
  Purchase #4 $202.48   13.797%   $230.4162   $230.42   $230.40   $230.40  
  Purchase #5 $203.92   9.735%   $223.7716   $223.77   $223.75   $223.80  
  Purchase #6 $44.47   3.474%   $46.0149   $46.01   $46.00   $46.00  
  Purchase #7 $118.74   5.869%   $125.7089   $125.71   $125.70   $125.70  
  7 purchase totals = $877.93       $955.0227   $955.03   $955.00   $955.00