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 $223.36   9.662%   $244.941   $244.94   $244.95   $244.90  
  Purchase #2 $230.78   7.492%   $248.07   $248.07   $248.05   $248.10  
  Purchase #3 $36.83   9.547%   $40.3462   $40.35   $40.35   $40.30  
  Purchase #4 $51.59   3.379%   $53.3332   $53.33   $53.35   $53.30  
  Purchase #5 $83.57   12.494%   $94.0112   $94.01   $94.00   $94.00  
  Purchase #6 $88.71   4.233%   $92.4651   $92.47   $92.45   $92.50  
  Purchase #7 $243.46   7.505%   $261.7317   $261.73   $261.75   $261.70  
  7 purchase totals = $958.30       $1,034.8984   $1,034.90   $1,034.90   $1,034.80