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 $186.53   11.485%   $207.953   $207.95   $207.95   $208.00  
  Purchase #2 $214.56   5.446%   $226.2449   $226.24   $226.25   $226.20  
  Purchase #3 $115.56   8.667%   $125.5756   $125.58   $125.60   $125.60  
  Purchase #4 $19.48   4.654%   $20.3866   $20.39   $20.40   $20.40  
  Purchase #5 $224.28   9.375%   $245.3063   $245.31   $245.30   $245.30  
  Purchase #6 $57.97   8.398%   $62.8383   $62.84   $62.85   $62.80  
  Purchase #7 $53.67   11.709%   $59.9542   $59.95   $59.95   $60.00  
  7 purchase totals = $872.05       $948.2589   $948.26   $948.30   $948.30