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 $88.48   8.444%   $95.9513   $95.95   $95.95   $96.00  
  Purchase #2 $185.48   6.494%   $197.5251   $197.53   $197.55   $197.50  
  Purchase #3 $249.49   12.202%   $279.9328   $279.93   $279.95   $279.90  
  Purchase #4 $133.70   12.798%   $150.8109   $150.81   $150.80   $150.80  
  Purchase #5 $132.39   5.225%   $139.3074   $139.31   $139.30   $139.30  
  Purchase #6 $217.88   11.470%   $242.8708   $242.87   $242.85   $242.90  
  Purchase #7 $5.95   6.682%   $6.3476   $6.35   $6.35   $6.30  
  7 purchase totals = $1,013.37       $1,112.7459   $1,112.75   $1,112.75   $1,112.70