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 $225.64   3.277%   $233.0342   $233.03   $233.05   $233.00  
  Purchase #2 $242.50   3.423%   $250.8008   $250.80   $250.80   $250.80  
  Purchase #3 $44.99   4.321%   $46.934   $46.93   $46.95   $46.90  
  Purchase #4 $178.84   10.534%   $197.679   $197.68   $197.70   $197.70  
  Purchase #5 $155.70   7.378%   $167.1875   $167.19   $167.20   $167.20  
  Purchase #6 $95.44   3.844%   $99.1087   $99.11   $99.10   $99.10  
  Purchase #7 $225.26   9.398%   $246.4299   $246.43   $246.45   $246.40  
  7 purchase totals = $1,168.37       $1,241.1741   $1,241.17   $1,241.25   $1,241.10