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 $231.65   8.455%   $251.236   $251.24   $251.25   $251.20  
  Purchase #2 $71.98   5.614%   $76.021   $76.02   $76.00   $76.00  
  Purchase #3 $250.97   11.189%   $279.051   $279.05   $279.05   $279.10  
  Purchase #4 $233.70   7.395%   $250.9821   $250.98   $251.00   $251.00  
  Purchase #5 $147.69   7.184%   $158.3   $158.30   $158.30   $158.30  
  Purchase #6 $170.69   7.666%   $183.7751   $183.78   $183.80   $183.80  
  Purchase #7 $182.29   7.617%   $196.175   $196.18   $196.20   $196.20  
  7 purchase totals = $1,288.97       $1,395.5402   $1,395.55   $1,395.60   $1,395.60