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 $244.99   7.445%   $263.2295   $263.23   $263.25   $263.20  
  Purchase #2 $146.92   3.371%   $151.8727   $151.87   $151.85   $151.90  
  Purchase #3 $98.75   13.375%   $111.9578   $111.96   $111.95   $112.00  
  Purchase #4 $222.62   4.662%   $232.9985   $233.00   $233.00   $233.00  
  Purchase #5 $249.85   13.861%   $284.4817   $284.48   $284.50   $284.50  
  Purchase #6 $202.81   9.300%   $221.6713   $221.67   $221.65   $221.70  
  Purchase #7 $185.74   4.564%   $194.2172   $194.22   $194.20   $194.20  
  7 purchase totals = $1,351.68       $1,460.4287   $1,460.43   $1,460.40   $1,460.50