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 $43.83   9.408%   $47.9535   $47.95   $47.95   $48.00  
  Purchase #2 $151.42   5.568%   $159.8511   $159.85   $159.85   $159.90  
  Purchase #3 $63.38   9.486%   $69.3922   $69.39   $69.40   $69.40  
  Purchase #4 $119.63   6.578%   $127.4993   $127.50   $127.50   $127.50  
  Purchase #5 $162.78   9.736%   $178.6283   $178.63   $178.65   $178.60  
  Purchase #6 $145.63   3.766%   $151.1144   $151.11   $151.10   $151.10  
  Purchase #7 $15.47   6.489%   $16.4738   $16.47   $16.45   $16.50  
  7 purchase totals = $702.14       $750.9126   $750.90   $750.90   $751.00