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 $245.43   6.628%   $261.6971   $261.70   $261.70   $261.70  
  Purchase #2 $101.94   7.648%   $109.7364   $109.74   $109.75   $109.70  
  Purchase #3 $86.47   9.603%   $94.7737   $94.77   $94.75   $94.80  
  Purchase #4 $103.92   4.631%   $108.7325   $108.73   $108.75   $108.70  
  Purchase #5 $73.38   5.783%   $77.6236   $77.62   $77.60   $77.60  
  Purchase #6 $58.62   7.644%   $63.1009   $63.10   $63.10   $63.10  
  Purchase #7 $55.49   3.738%   $57.5642   $57.56   $57.55   $57.60  
  7 purchase totals = $725.25       $773.2284   $773.22   $773.20   $773.20