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 $114.40   4.149%   $119.1465   $119.15   $119.15   $119.10  
  Purchase #2 $175.88   8.707%   $191.1939   $191.19   $191.20   $191.20  
  Purchase #3 $40.51   4.150%   $42.1912   $42.19   $42.20   $42.20  
  Purchase #4 $117.83   3.752%   $122.251   $122.25   $122.25   $122.30  
  Purchase #5 $203.71   9.620%   $223.3069   $223.31   $223.30   $223.30  
  Purchase #6 $239.64   8.459%   $259.9111   $259.91   $259.90   $259.90  
  Purchase #7 $62.68   3.304%   $64.7509   $64.75   $64.75   $64.80  
  7 purchase totals = $954.65       $1,022.7515   $1,022.75   $1,022.75   $1,022.80