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 $42.92   10.690%   $47.5081   $47.51   $47.50   $47.50  
  Purchase #2 $215.63   8.452%   $233.855   $233.86   $233.85   $233.90  
  Purchase #3 $224.98   4.361%   $234.7914   $234.79   $234.80   $234.80  
  Purchase #4 $192.98   7.847%   $208.1231   $208.12   $208.10   $208.10  
  Purchase #5 $56.64   12.388%   $63.6566   $63.66   $63.65   $63.70  
  Purchase #6 $14.64   7.119%   $15.6822   $15.68   $15.70   $15.70  
  Purchase #7 $205.35   11.639%   $229.2507   $229.25   $229.25   $229.30  
  7 purchase totals = $953.14       $1,032.8671   $1,032.87   $1,032.85   $1,033.00