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 $84.88   12.242%   $95.271   $95.27   $95.25   $95.30  
  Purchase #2 $27.27   6.518%   $29.0475   $29.05   $29.05   $29.00  
  Purchase #3 $207.56   9.184%   $226.6223   $226.62   $226.60   $226.60  
  Purchase #4 $35.27   5.787%   $37.3111   $37.31   $37.30   $37.30  
  Purchase #5 $201.90   3.223%   $208.4072   $208.41   $208.40   $208.40  
  Purchase #6 $49.88   3.839%   $51.7949   $51.79   $51.80   $51.80  
  Purchase #7 $81.42   3.203%   $84.0279   $84.03   $84.05   $84.00  
  7 purchase totals = $688.18       $732.4819   $732.48   $732.45   $732.40