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 $67.29   9.428%   $73.6341   $73.63   $73.65   $73.60  
  Purchase #2 $25.91   8.526%   $28.1191   $28.12   $28.10   $28.10  
  Purchase #3 $147.83   5.452%   $155.8897   $155.89   $155.90   $155.90  
  Purchase #4 $240.89   8.644%   $261.7125   $261.71   $261.70   $261.70  
  Purchase #5 $232.82   3.607%   $241.2178   $241.22   $241.20   $241.20  
  Purchase #6 $235.60   11.413%   $262.489   $262.49   $262.50   $262.50  
  Purchase #7 $216.54   8.743%   $235.4721   $235.47   $235.45   $235.50  
  7 purchase totals = $1,166.88       $1,258.5343   $1,258.53   $1,258.50   $1,258.50