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 $237.88   12.368%   $267.301   $267.30   $267.30   $267.30  
  Purchase #2 $91.40   4.703%   $95.6985   $95.70   $95.70   $95.70  
  Purchase #3 $167.75   6.739%   $179.0547   $179.05   $179.05   $179.10  
  Purchase #4 $213.85   9.227%   $233.5819   $233.58   $233.60   $233.60  
  Purchase #5 $241.35   4.863%   $253.0869   $253.09   $253.10   $253.10  
  Purchase #6 $191.64   11.414%   $213.5138   $213.51   $213.50   $213.50  
  Purchase #7 $119.60   3.605%   $123.9116   $123.91   $123.90   $123.90  
  7 purchase totals = $1,263.47       $1,366.1484   $1,366.14   $1,366.15   $1,366.20