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 $118.56   5.852%   $125.4981   $125.50   $125.50   $125.50  
  Purchase #2 $41.41   9.166%   $45.2056   $45.21   $45.20   $45.20  
  Purchase #3 $211.27   10.772%   $234.028   $234.03   $234.05   $234.00  
  Purchase #4 $53.96   6.283%   $57.3503   $57.35   $57.35   $57.40  
  Purchase #5 $147.39   8.733%   $160.2616   $160.26   $160.25   $160.30  
  Purchase #6 $44.68   9.550%   $48.9469   $48.95   $48.95   $48.90  
  Purchase #7 $78.77   4.150%   $82.039   $82.04   $82.05   $82.00  
  7 purchase totals = $696.04       $753.3295   $753.34   $753.35   $753.30