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 $211.53   7.667%   $227.748   $227.75   $227.75   $227.70  
  Purchase #2 $5.67   7.597%   $6.1007   $6.10   $6.10   $6.10  
  Purchase #3 $33.43   3.146%   $34.4817   $34.48   $34.50   $34.50  
  Purchase #4 $52.65   9.605%   $57.707   $57.71   $57.70   $57.70  
  Purchase #5 $53.71   9.585%   $58.8581   $58.86   $58.85   $58.90  
  Purchase #6 $67.56   12.262%   $75.8442   $75.84   $75.85   $75.80  
  Purchase #7 $7.35   4.772%   $7.7007   $7.70   $7.70   $7.70  
  7 purchase totals = $431.90       $468.4404   $468.44   $468.45   $468.40