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 $62.86   3.361%   $64.9727   $64.97   $64.95   $65.00  
  Purchase #2 $219.73   11.330%   $244.6254   $244.63   $244.65   $244.60  
  Purchase #3 $155.35   6.815%   $165.9371   $165.94   $165.95   $165.90  
  Purchase #4 $126.64   8.223%   $137.0536   $137.05   $137.05   $137.10  
  Purchase #5 $194.53   3.870%   $202.0583   $202.06   $202.05   $202.10  
  Purchase #6 $178.83   10.151%   $196.983   $196.98   $197.00   $197.00  
  Purchase #7 $232.93   3.388%   $240.8217   $240.82   $240.80   $240.80  
  7 purchase totals = $1,170.87       $1,252.4518   $1,252.45   $1,252.45   $1,252.50