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 $175.72   13.833%   $200.0273   $200.03   $200.05   $200.00  
  Purchase #2 $32.63   8.145%   $35.2877   $35.29   $35.30   $35.30  
  Purchase #3 $212.30   3.528%   $219.7899   $219.79   $219.80   $219.80  
  Purchase #4 $21.42   7.489%   $23.0241   $23.02   $23.00   $23.00  
  Purchase #5 $59.46   10.428%   $65.6605   $65.66   $65.65   $65.70  
  Purchase #6 $176.60   7.754%   $190.2936   $190.29   $190.30   $190.30  
  Purchase #7 $23.28   9.106%   $25.3999   $25.40   $25.40   $25.40  
  7 purchase totals = $701.41       $759.4830   $759.48   $759.50   $759.50