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 $164.45   10.679%   $182.0116   $182.01   $182.00   $182.00  
  Purchase #2 $82.46   13.798%   $93.8378   $93.84   $93.85   $93.80  
  Purchase #3 $23.38   3.547%   $24.2093   $24.21   $24.20   $24.20  
  Purchase #4 $93.42   8.267%   $101.143   $101.14   $101.15   $101.10  
  Purchase #5 $190.45   10.506%   $210.4587   $210.46   $210.45   $210.50  
  Purchase #6 $93.85   5.480%   $98.993   $98.99   $99.00   $99.00  
  Purchase #7 $245.95   3.647%   $254.9198   $254.92   $254.90   $254.90  
  7 purchase totals = $893.96       $965.5732   $965.57   $965.55   $965.50