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 $153.57   8.567%   $166.7263   $166.73   $166.75   $166.70  
  Purchase #2 $127.94   12.314%   $143.6945   $143.69   $143.70   $143.70  
  Purchase #3 $62.55   12.486%   $70.36   $70.36   $70.35   $70.40  
  Purchase #4 $244.29   9.455%   $267.3876   $267.39   $267.40   $267.40  
  Purchase #5 $152.98   4.169%   $159.3577   $159.36   $159.35   $159.40  
  Purchase #6 $213.95   5.112%   $224.8871   $224.89   $224.90   $224.90  
  Purchase #7 $150.92   7.262%   $161.8798   $161.88   $161.90   $161.90  
  7 purchase totals = $1,106.20       $1,194.2930   $1,194.30   $1,194.35   $1,194.40