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 $207.56   11.763%   $231.9753   $231.98   $232.00   $232.00  
  Purchase #2 $62.91   5.431%   $66.3266   $66.33   $66.35   $66.30  
  Purchase #3 $72.34   5.684%   $76.4518   $76.45   $76.45   $76.50  
  Purchase #4 $162.63   8.409%   $176.3056   $176.31   $176.30   $176.30  
  Purchase #5 $249.99   4.318%   $260.7846   $260.78   $260.80   $260.80  
  Purchase #6 $156.66   11.654%   $174.9172   $174.92   $174.90   $174.90  
  Purchase #7 $191.62   3.515%   $198.3554   $198.36   $198.35   $198.40  
  7 purchase totals = $1,103.71       $1,185.1165   $1,185.13   $1,185.15   $1,185.20