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 $151.46   8.465%   $164.2811   $164.28   $164.30   $164.30  
  Purchase #2 $204.69   6.348%   $217.6837   $217.68   $217.70   $217.70  
  Purchase #3 $216.90   11.821%   $242.5397   $242.54   $242.55   $242.50  
  Purchase #4 $195.36   5.803%   $206.6967   $206.70   $206.70   $206.70  
  Purchase #5 $60.77   6.854%   $64.9352   $64.94   $64.95   $64.90  
  Purchase #6 $21.90   11.838%   $24.4925   $24.49   $24.50   $24.50  
  Purchase #7 $167.36   9.200%   $182.7571   $182.76   $182.75   $182.80  
  7 purchase totals = $1,018.44       $1,103.3860   $1,103.39   $1,103.45   $1,103.40