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 $214.77   11.128%   $238.6696   $238.67   $238.65   $238.70  
  Purchase #2 $234.93   5.714%   $248.3539   $248.35   $248.35   $248.40  
  Purchase #3 $205.26   5.841%   $217.2492   $217.25   $217.25   $217.20  
  Purchase #4 $214.52   8.119%   $231.9369   $231.94   $231.95   $231.90  
  Purchase #5 $115.52   10.277%   $127.392   $127.39   $127.40   $127.40  
  Purchase #6 $9.51   3.683%   $9.8603   $9.86   $9.85   $9.90  
  Purchase #7 $192.80   3.373%   $199.3031   $199.30   $199.30   $199.30  
  7 purchase totals = $1,187.31       $1,272.7650   $1,272.76   $1,272.75   $1,272.80