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 $60.60   8.407%   $65.6946   $65.69   $65.70   $65.70  
  Purchase #2 $11.34   5.248%   $11.9351   $11.94   $11.95   $11.90  
  Purchase #3 $88.71   7.271%   $95.1601   $95.16   $95.15   $95.20  
  Purchase #4 $44.93   6.271%   $47.7476   $47.75   $47.75   $47.70  
  Purchase #5 $96.71   8.712%   $105.1354   $105.14   $105.15   $105.10  
  Purchase #6 $218.52   8.125%   $236.2748   $236.27   $236.25   $236.30  
  Purchase #7 $170.41   8.198%   $184.3802   $184.38   $184.40   $184.40  
  7 purchase totals = $691.22       $746.3278   $746.33   $746.35   $746.30