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 $196.86   4.232%   $205.1911   $205.19   $205.20   $205.20  
  Purchase #2 $164.34   13.105%   $185.8768   $185.88   $185.90   $185.90  
  Purchase #3 $21.97   3.784%   $22.8013   $22.80   $22.80   $22.80  
  Purchase #4 $182.41   5.170%   $191.8406   $191.84   $191.85   $191.80  
  Purchase #5 $86.73   5.714%   $91.6858   $91.69   $91.70   $91.70  
  Purchase #6 $123.32   7.507%   $132.5776   $132.58   $132.60   $132.60  
  Purchase #7 $206.40   11.128%   $229.3682   $229.37   $229.35   $229.40  
  7 purchase totals = $982.03       $1,059.3414   $1,059.35   $1,059.40   $1,059.40