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 $204.83   9.456%   $224.1987   $224.20   $224.20   $224.20  
  Purchase #2 $236.28   13.556%   $268.3101   $268.31   $268.30   $268.30  
  Purchase #3 $217.59   12.338%   $244.4363   $244.44   $244.45   $244.40  
  Purchase #4 $98.37   10.672%   $108.868   $108.87   $108.85   $108.90  
  Purchase #5 $201.63   4.595%   $210.8949   $210.89   $210.90   $210.90  
  Purchase #6 $192.94   9.717%   $211.688   $211.69   $211.70   $211.70  
  Purchase #7 $180.60   7.672%   $194.4556   $194.46   $194.45   $194.50  
  7 purchase totals = $1,332.24       $1,462.8516   $1,462.86   $1,462.85   $1,462.90