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 $116.93   7.138%   $125.2765   $125.28   $125.30   $125.30  
  Purchase #2 $126.53   3.795%   $131.3318   $131.33   $131.35   $131.30  
  Purchase #3 $92.33   7.808%   $99.5391   $99.54   $99.55   $99.50  
  Purchase #4 $146.60   11.694%   $163.7434   $163.74   $163.75   $163.70  
  Purchase #5 $156.83   3.245%   $161.9191   $161.92   $161.90   $161.90  
  Purchase #6 $241.85   10.684%   $267.6893   $267.69   $267.70   $267.70  
  Purchase #7 $58.37   10.652%   $64.5876   $64.59   $64.60   $64.60  
  7 purchase totals = $939.44       $1,014.0868   $1,014.09   $1,014.15   $1,014.00