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 $58.82   7.569%   $63.2721   $63.27   $63.25   $63.30  
  Purchase #2 $226.41   11.201%   $251.7702   $251.77   $251.75   $251.80  
  Purchase #3 $209.25   11.582%   $233.4853   $233.49   $233.50   $233.50  
  Purchase #4 $92.93   10.350%   $102.5483   $102.55   $102.55   $102.50  
  Purchase #5 $130.79   4.621%   $136.8338   $136.83   $136.85   $136.80  
  Purchase #6 $138.76   11.507%   $154.7271   $154.73   $154.75   $154.70  
  Purchase #7 $143.37   12.816%   $161.7443   $161.74   $161.75   $161.70  
  7 purchase totals = $1,000.33       $1,104.3811   $1,104.38   $1,104.40   $1,104.30