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 $86.68   9.362%   $94.795   $94.80   $94.80   $94.80  
  Purchase #2 $217.51   11.356%   $242.2104   $242.21   $242.20   $242.20  
  Purchase #3 $118.72   6.373%   $126.286   $126.29   $126.30   $126.30  
  Purchase #4 $118.73   11.667%   $132.5822   $132.58   $132.60   $132.60  
  Purchase #5 $187.60   3.863%   $194.847   $194.85   $194.85   $194.80  
  Purchase #6 $170.66   4.523%   $178.379   $178.38   $178.40   $178.40  
  Purchase #7 $50.55   9.730%   $55.4685   $55.47   $55.45   $55.50  
  7 purchase totals = $950.45       $1,024.5681   $1,024.58   $1,024.60   $1,024.60