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 $59.78   4.828%   $62.6662   $62.67   $62.65   $62.70  
  Purchase #2 $124.77   6.317%   $132.6517   $132.65   $132.65   $132.70  
  Purchase #3 $102.78   4.256%   $107.1543   $107.15   $107.15   $107.20  
  Purchase #4 $103.86   6.193%   $110.292   $110.29   $110.30   $110.30  
  Purchase #5 $29.47   6.328%   $31.3349   $31.33   $31.35   $31.30  
  Purchase #6 $94.65   4.622%   $99.0247   $99.02   $99.00   $99.00  
  Purchase #7 $163.58   7.362%   $175.6228   $175.62   $175.60   $175.60  
  7 purchase totals = $678.89       $718.7466   $718.73   $718.70   $718.80