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 $136.81   11.835%   $153.0015   $153.00   $153.00   $153.00  
  Purchase #2 $221.53   10.227%   $244.1859   $244.19   $244.20   $244.20  
  Purchase #3 $59.34   10.726%   $65.7048   $65.70   $65.70   $65.70  
  Purchase #4 $172.66   5.527%   $182.2029   $182.20   $182.20   $182.20  
  Purchase #5 $46.87   10.297%   $51.6962   $51.70   $51.70   $51.70  
  Purchase #6 $199.49   4.377%   $208.2217   $208.22   $208.20   $208.20  
  Purchase #7 $197.93   9.739%   $217.2064   $217.21   $217.20   $217.20  
  7 purchase totals = $1,034.63       $1,122.2194   $1,122.22   $1,122.20   $1,122.20