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 $182.69   7.432%   $196.2675   $196.27   $196.25   $196.30  
  Purchase #2 $13.93   3.136%   $14.3668   $14.37   $14.35   $14.40  
  Purchase #3 $207.51   3.713%   $215.2148   $215.21   $215.20   $215.20  
  Purchase #4 $60.34   12.614%   $67.9513   $67.95   $67.95   $68.00  
  Purchase #5 $125.83   3.817%   $130.6329   $130.63   $130.65   $130.60  
  Purchase #6 $127.74   3.301%   $131.9567   $131.96   $131.95   $132.00  
  Purchase #7 $185.44   13.468%   $210.4151   $210.42   $210.40   $210.40  
  7 purchase totals = $903.48       $966.8051   $966.81   $966.75   $966.90