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 $118.63   6.195%   $125.9791   $125.98   $126.00   $126.00  
  Purchase #2 $57.75   9.669%   $63.3338   $63.33   $63.35   $63.30  
  Purchase #3 $87.59   8.680%   $95.1928   $95.19   $95.20   $95.20  
  Purchase #4 $195.98   7.114%   $209.922   $209.92   $209.90   $209.90  
  Purchase #5 $197.66   6.550%   $210.6067   $210.61   $210.60   $210.60  
  Purchase #6 $104.73   6.834%   $111.8872   $111.89   $111.90   $111.90  
  Purchase #7 $214.67   4.774%   $224.9183   $224.92   $224.90   $224.90  
  7 purchase totals = $977.01       $1,041.8399   $1,041.84   $1,041.85   $1,041.80