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 $192.43   11.859%   $215.2503   $215.25   $215.25   $215.30  
  Purchase #2 $118.78   5.531%   $125.3497   $125.35   $125.35   $125.30  
  Purchase #3 $157.73   13.827%   $179.5393   $179.54   $179.55   $179.50  
  Purchase #4 $219.58   11.652%   $245.1655   $245.17   $245.15   $245.20  
  Purchase #5 $66.91   10.677%   $74.054   $74.05   $74.05   $74.10  
  Purchase #6 $53.87   13.586%   $61.1888   $61.19   $61.20   $61.20  
  Purchase #7 $210.57   3.823%   $218.6201   $218.62   $218.60   $218.60  
  7 purchase totals = $1,019.87       $1,119.1677   $1,119.17   $1,119.15   $1,119.20