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 $83.99   12.699%   $94.6559   $94.66   $94.65   $94.70  
  Purchase #2 $214.65   10.790%   $237.8107   $237.81   $237.80   $237.80  
  Purchase #3 $67.38   8.144%   $72.8674   $72.87   $72.85   $72.90  
  Purchase #4 $9.74   8.658%   $10.5833   $10.58   $10.60   $10.60  
  Purchase #5 $119.94   4.572%   $125.4237   $125.42   $125.40   $125.40  
  Purchase #6 $212.57   5.843%   $224.9905   $224.99   $225.00   $225.00  
  Purchase #7 $31.68   12.347%   $35.5915   $35.59   $35.60   $35.60  
  7 purchase totals = $739.95       $801.9230   $801.92   $801.90   $802.00