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 $68.36   7.225%   $73.299   $73.30   $73.30   $73.30  
  Purchase #2 $217.29   3.609%   $225.132   $225.13   $225.15   $225.10  
  Purchase #3 $123.41   7.500%   $132.6658   $132.67   $132.65   $132.70  
  Purchase #4 $241.66   9.406%   $264.3905   $264.39   $264.40   $264.40  
  Purchase #5 $144.62   13.120%   $163.5941   $163.59   $163.60   $163.60  
  Purchase #6 $235.63   13.656%   $267.8076   $267.81   $267.80   $267.80  
  Purchase #7 $83.76   12.689%   $94.3883   $94.39   $94.40   $94.40  
  7 purchase totals = $1,114.73       $1,221.2773   $1,221.28   $1,221.30   $1,221.30