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 $164.30   6.756%   $175.4001   $175.40   $175.40   $175.40  
  Purchase #2 $223.53   5.377%   $235.5492   $235.55   $235.55   $235.50  
  Purchase #3 $40.82   11.754%   $45.618   $45.62   $45.60   $45.60  
  Purchase #4 $203.31   8.189%   $219.9591   $219.96   $219.95   $220.00  
  Purchase #5 $124.72   13.313%   $141.324   $141.32   $141.30   $141.30  
  Purchase #6 $115.79   8.476%   $125.6044   $125.60   $125.60   $125.60  
  Purchase #7 $19.83   10.290%   $21.8705   $21.87   $21.85   $21.90  
  7 purchase totals = $892.30       $965.3253   $965.32   $965.25   $965.30