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 $217.27   4.600%   $227.2644   $227.26   $227.25   $227.30  
  Purchase #2 $124.67   7.211%   $133.66   $133.66   $133.65   $133.70  
  Purchase #3 $61.72   3.512%   $63.8876   $63.89   $63.90   $63.90  
  Purchase #4 $244.37   5.176%   $257.0186   $257.02   $257.00   $257.00  
  Purchase #5 $80.83   8.451%   $87.6609   $87.66   $87.65   $87.70  
  Purchase #6 $10.67   11.317%   $11.8775   $11.88   $11.90   $11.90  
  Purchase #7 $142.70   12.145%   $160.0309   $160.03   $160.05   $160.00  
  7 purchase totals = $882.23       $941.3999   $941.40   $941.40   $941.50