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 $92.65   4.164%   $96.5079   $96.51   $96.50   $96.50  
  Purchase #2 $135.78   9.118%   $148.1604   $148.16   $148.15   $148.20  
  Purchase #3 $57.64   4.441%   $60.1998   $60.20   $60.20   $60.20  
  Purchase #4 $198.51   9.567%   $217.5015   $217.50   $217.50   $217.50  
  Purchase #5 $125.52   4.175%   $130.7605   $130.76   $130.75   $130.80  
  Purchase #6 $232.60   8.485%   $252.3361   $252.34   $252.35   $252.30  
  Purchase #7 $39.94   9.664%   $43.7998   $43.80   $43.80   $43.80  
  7 purchase totals = $882.64       $949.2660   $949.27   $949.25   $949.30