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 $132.61   8.601%   $144.0158   $144.02   $144.00   $144.00  
  Purchase #2 $206.95   7.614%   $222.7072   $222.71   $222.70   $222.70  
  Purchase #3 $119.28   6.243%   $126.7267   $126.73   $126.75   $126.70  
  Purchase #4 $215.61   10.714%   $238.7105   $238.71   $238.70   $238.70  
  Purchase #5 $119.34   10.450%   $131.811   $131.81   $131.80   $131.80  
  Purchase #6 $132.95   4.213%   $138.5512   $138.55   $138.55   $138.60  
  Purchase #7 $183.84   4.210%   $191.5797   $191.58   $191.60   $191.60  
  7 purchase totals = $1,110.58       $1,194.1021   $1,194.11   $1,194.10   $1,194.10