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 $214.37   13.273%   $242.8233   $242.82   $242.80   $242.80  
  Purchase #2 $190.64   6.838%   $203.676   $203.68   $203.70   $203.70  
  Purchase #3 $43.47   6.489%   $46.2908   $46.29   $46.30   $46.30  
  Purchase #4 $172.65   13.770%   $196.4239   $196.42   $196.40   $196.40  
  Purchase #5 $95.40   6.124%   $101.2423   $101.24   $101.25   $101.20  
  Purchase #6 $215.70   12.815%   $243.342   $243.34   $243.35   $243.30  
  Purchase #7 $241.62   8.866%   $263.042   $263.04   $263.05   $263.00  
  7 purchase totals = $1,173.85       $1,296.8403   $1,296.83   $1,296.85   $1,296.70