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 $201.80   5.706%   $213.3147   $213.31   $213.30   $213.30  
  Purchase #2 $232.38   9.209%   $253.7799   $253.78   $253.80   $253.80  
  Purchase #3 $40.38   13.855%   $45.9746   $45.97   $45.95   $46.00  
  Purchase #4 $79.36   4.804%   $83.1725   $83.17   $83.15   $83.20  
  Purchase #5 $245.90   8.246%   $266.1769   $266.18   $266.20   $266.20  
  Purchase #6 $62.71   3.437%   $64.8653   $64.87   $64.85   $64.90  
  Purchase #7 $160.68   10.475%   $177.5112   $177.51   $177.50   $177.50  
  7 purchase totals = $1,023.21       $1,104.7951   $1,104.79   $1,104.75   $1,104.90