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 $171.75   5.725%   $181.5827   $181.58   $181.60   $181.60  
  Purchase #2 $62.36   9.128%   $68.0522   $68.05   $68.05   $68.10  
  Purchase #3 $250.92   5.730%   $265.2977   $265.30   $265.30   $265.30  
  Purchase #4 $107.63   11.380%   $119.8783   $119.88   $119.90   $119.90  
  Purchase #5 $123.44   8.109%   $133.4497   $133.45   $133.45   $133.40  
  Purchase #6 $195.58   4.350%   $204.0877   $204.09   $204.10   $204.10  
  Purchase #7 $164.64   6.674%   $175.6281   $175.63   $175.65   $175.60  
  7 purchase totals = $1,076.32       $1,147.9764   $1,147.98   $1,148.05   $1,148.00