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 $184.78   5.658%   $195.2349   $195.23   $195.25   $195.20  
  Purchase #2 $223.28   7.308%   $239.5973   $239.60   $239.60   $239.60  
  Purchase #3 $236.91   4.858%   $248.4191   $248.42   $248.40   $248.40  
  Purchase #4 $26.98   13.105%   $30.5157   $30.52   $30.50   $30.50  
  Purchase #5 $107.59   7.508%   $115.6679   $115.67   $115.65   $115.70  
  Purchase #6 $233.51   11.700%   $260.8307   $260.83   $260.85   $260.80  
  Purchase #7 $61.57   9.381%   $67.3459   $67.35   $67.35   $67.30  
  7 purchase totals = $1,074.62       $1,157.6115   $1,157.62   $1,157.60   $1,157.50