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 $44.33   8.250%   $47.9872   $47.99   $48.00   $48.00  
  Purchase #2 $199.64   4.614%   $208.8514   $208.85   $208.85   $208.90  
  Purchase #3 $109.70   8.497%   $119.0212   $119.02   $119.00   $119.00  
  Purchase #4 $194.40   11.489%   $216.7346   $216.73   $216.75   $216.70  
  Purchase #5 $213.99   11.328%   $238.2308   $238.23   $238.25   $238.20  
  Purchase #6 $43.50   5.750%   $46.0013   $46.00   $46.00   $46.00  
  Purchase #7 $142.33   9.804%   $156.284   $156.28   $156.30   $156.30  
  7 purchase totals = $947.89       $1,033.1105   $1,033.10   $1,033.15   $1,033.10