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 $44.68   3.327%   $46.1665   $46.17   $46.15   $46.20  
  Purchase #2 $213.96   11.846%   $239.3057   $239.31   $239.30   $239.30  
  Purchase #3 $152.39   5.222%   $160.3478   $160.35   $160.35   $160.30  
  Purchase #4 $173.31   13.419%   $196.5665   $196.57   $196.55   $196.60  
  Purchase #5 $203.59   13.772%   $231.6284   $231.63   $231.65   $231.60  
  Purchase #6 $185.74   10.632%   $205.4879   $205.49   $205.50   $205.50  
  Purchase #7 $226.37   4.655%   $236.9075   $236.91   $236.90   $236.90  
  7 purchase totals = $1,200.04       $1,316.4103   $1,316.43   $1,316.40   $1,316.40