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 $97.62   5.123%   $102.6211   $102.62   $102.60   $102.60  
  Purchase #2 $119.66   5.261%   $125.9553   $125.96   $125.95   $126.00  
  Purchase #3 $243.30   11.695%   $271.7539   $271.75   $271.75   $271.80  
  Purchase #4 $248.92   11.492%   $277.5259   $277.53   $277.55   $277.50  
  Purchase #5 $65.58   5.859%   $69.4223   $69.42   $69.40   $69.40  
  Purchase #6 $133.58   4.361%   $139.4054   $139.41   $139.40   $139.40  
  Purchase #7 $58.51   9.763%   $64.2223   $64.22   $64.20   $64.20  
  7 purchase totals = $967.17       $1,050.9062   $1,050.91   $1,050.85   $1,050.90