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 $244.53   7.631%   $263.1901   $263.19   $263.20   $263.20  
  Purchase #2 $194.66   10.685%   $215.4594   $215.46   $215.45   $215.50  
  Purchase #3 $158.81   7.863%   $171.2972   $171.30   $171.30   $171.30  
  Purchase #4 $184.72   11.662%   $206.262   $206.26   $206.25   $206.30  
  Purchase #5 $99.70   6.768%   $106.4477   $106.45   $106.45   $106.40  
  Purchase #6 $170.28   7.679%   $183.3558   $183.36   $183.35   $183.40  
  Purchase #7 $117.27   4.422%   $122.4557   $122.46   $122.45   $122.50  
  7 purchase totals = $1,169.97       $1,268.4679   $1,268.48   $1,268.45   $1,268.60