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 $65.40   9.216%   $71.4273   $71.43   $71.45   $71.40  
  Purchase #2 $47.56   6.191%   $50.5044   $50.50   $50.50   $50.50  
  Purchase #3 $171.81   12.597%   $193.4529   $193.45   $193.45   $193.50  
  Purchase #4 $68.44   10.385%   $75.5475   $75.55   $75.55   $75.50  
  Purchase #5 $110.95   7.774%   $119.5753   $119.58   $119.60   $119.60  
  Purchase #6 $205.99   4.513%   $215.2863   $215.29   $215.30   $215.30  
  Purchase #7 $58.26   4.172%   $60.6906   $60.69   $60.70   $60.70  
  7 purchase totals = $728.41       $786.4843   $786.49   $786.55   $786.50