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 $91.67   3.276%   $94.6731   $94.67   $94.65   $94.70  
  Purchase #2 $199.48   8.182%   $215.8015   $215.80   $215.80   $215.80  
  Purchase #3 $215.32   4.724%   $225.4917   $225.49   $225.50   $225.50  
  Purchase #4 $207.77   12.856%   $234.4809   $234.48   $234.50   $234.50  
  Purchase #5 $101.66   10.368%   $112.2001   $112.20   $112.20   $112.20  
  Purchase #6 $225.31   3.432%   $233.0426   $233.04   $233.05   $233.00  
  Purchase #7 $98.88   11.132%   $109.8873   $109.89   $109.90   $109.90  
  7 purchase totals = $1,140.09       $1,225.5772   $1,225.57   $1,225.60   $1,225.60