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 $95.29   3.105%   $98.2488   $98.25   $98.25   $98.20  
  Purchase #2 $186.52   5.576%   $196.9204   $196.92   $196.90   $196.90  
  Purchase #3 $186.66   5.793%   $197.4732   $197.47   $197.45   $197.50  
  Purchase #4 $199.39   11.437%   $222.1942   $222.19   $222.20   $222.20  
  Purchase #5 $96.34   11.571%   $107.4875   $107.49   $107.50   $107.50  
  Purchase #6 $67.97   13.513%   $77.1548   $77.15   $77.15   $77.20  
  Purchase #7 $198.74   13.376%   $225.3235   $225.32   $225.30   $225.30  
  7 purchase totals = $1,030.91       $1,124.8024   $1,124.79   $1,124.75   $1,124.80