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 $244.52   7.149%   $262.0007   $262.00   $262.00   $262.00  
  Purchase #2 $213.84   13.687%   $243.1083   $243.11   $243.10   $243.10  
  Purchase #3 $117.43   13.549%   $133.3406   $133.34   $133.35   $133.30  
  Purchase #4 $231.82   6.209%   $246.2137   $246.21   $246.20   $246.20  
  Purchase #5 $18.25   8.282%   $19.7615   $19.76   $19.75   $19.80  
  Purchase #6 $78.74   4.173%   $82.0258   $82.03   $82.05   $82.00  
  Purchase #7 $163.66   3.138%   $168.7957   $168.80   $168.80   $168.80  
  7 purchase totals = $1,068.26       $1,155.2463   $1,155.25   $1,155.25   $1,155.20