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 $215.29   5.450%   $227.0233   $227.02   $227.00   $227.00  
  Purchase #2 $207.46   13.731%   $235.9463   $235.95   $235.95   $235.90  
  Purchase #3 $86.88   12.797%   $97.998   $98.00   $98.00   $98.00  
  Purchase #4 $96.29   5.291%   $101.3847   $101.38   $101.40   $101.40  
  Purchase #5 $70.75   3.623%   $73.3133   $73.31   $73.30   $73.30  
  Purchase #6 $88.90   8.550%   $96.501   $96.50   $96.50   $96.50  
  Purchase #7 $93.25   4.234%   $97.1982   $97.20   $97.20   $97.20  
  7 purchase totals = $858.82       $929.3648   $929.36   $929.35   $929.30