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 $202.36   6.228%   $214.963   $214.96   $214.95   $215.00  
  Purchase #2 $71.42   11.158%   $79.389   $79.39   $79.40   $79.40  
  Purchase #3 $131.58   11.443%   $146.6367   $146.64   $146.65   $146.60  
  Purchase #4 $171.80   12.771%   $193.7406   $193.74   $193.75   $193.70  
  Purchase #5 $75.53   11.862%   $84.4894   $84.49   $84.50   $84.50  
  Purchase #6 $131.86   7.418%   $141.6414   $141.64   $141.65   $141.60  
  Purchase #7 $92.43   9.759%   $101.4502   $101.45   $101.45   $101.50  
  7 purchase totals = $876.98       $962.3103   $962.31   $962.35   $962.30