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 $80.95   13.602%   $91.9608   $91.96   $91.95   $92.00  
  Purchase #2 $13.59   7.566%   $14.6182   $14.62   $14.60   $14.60  
  Purchase #3 $132.94   11.821%   $148.6548   $148.65   $148.65   $148.70  
  Purchase #4 $211.73   5.318%   $222.9898   $222.99   $223.00   $223.00  
  Purchase #5 $142.59   10.454%   $157.4964   $157.50   $157.50   $157.50  
  Purchase #6 $14.25   8.559%   $15.4697   $15.47   $15.45   $15.50  
  Purchase #7 $87.60   8.137%   $94.728   $94.73   $94.75   $94.70  
  7 purchase totals = $683.65       $745.9177   $745.92   $745.90   $746.00