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 $44.39   11.168%   $49.3475   $49.35   $49.35   $49.30  
  Purchase #2 $42.42   9.331%   $46.3782   $46.38   $46.40   $46.40  
  Purchase #3 $213.41   9.612%   $233.923   $233.92   $233.90   $233.90  
  Purchase #4 $92.72   4.560%   $96.948   $96.95   $96.95   $96.90  
  Purchase #5 $177.72   4.644%   $185.9733   $185.97   $185.95   $186.00  
  Purchase #6 $239.58   10.204%   $264.0267   $264.03   $264.05   $264.00  
  Purchase #7 $212.30   7.754%   $228.7617   $228.76   $228.75   $228.80  
  7 purchase totals = $1,022.54       $1,105.3584   $1,105.36   $1,105.35   $1,105.30