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 $60.94   7.502%   $65.5117   $65.51   $65.50   $65.50  
  Purchase #2 $218.88   11.729%   $244.5524   $244.55   $244.55   $244.60  
  Purchase #3 $162.38   12.223%   $182.2277   $182.23   $182.25   $182.20  
  Purchase #4 $56.58   9.662%   $62.0468   $62.05   $62.05   $62.00  
  Purchase #5 $170.64   9.646%   $187.0999   $187.10   $187.10   $187.10  
  Purchase #6 $39.81   12.417%   $44.7532   $44.75   $44.75   $44.80  
  Purchase #7 $249.47   13.186%   $282.3651   $282.37   $282.35   $282.40  
  7 purchase totals = $958.70       $1,068.5568   $1,068.56   $1,068.55   $1,068.60