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 $182.64   7.491%   $196.3216   $196.32   $196.30   $196.30  
  Purchase #2 $65.71   6.422%   $69.9299   $69.93   $69.95   $69.90  
  Purchase #3 $169.99   13.189%   $192.41   $192.41   $192.40   $192.40  
  Purchase #4 $52.77   13.368%   $59.8243   $59.82   $59.80   $59.80  
  Purchase #5 $80.48   8.466%   $87.2934   $87.29   $87.30   $87.30  
  Purchase #6 $226.95   8.287%   $245.7573   $245.76   $245.75   $245.80  
  Purchase #7 $145.84   8.835%   $158.725   $158.73   $158.75   $158.70  
  7 purchase totals = $924.38       $1,010.2615   $1,010.26   $1,010.25   $1,010.20