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 $212.66   5.297%   $223.9246   $223.92   $223.90   $223.90  
  Purchase #2 $24.48   7.567%   $26.3324   $26.33   $26.35   $26.30  
  Purchase #3 $72.76   5.826%   $76.999   $77.00   $77.00   $77.00  
  Purchase #4 $206.56   3.673%   $214.1469   $214.15   $214.15   $214.10  
  Purchase #5 $170.76   9.598%   $187.1495   $187.15   $187.15   $187.10  
  Purchase #6 $228.29   13.614%   $259.3694   $259.37   $259.35   $259.40  
  Purchase #7 $66.81   10.253%   $73.66   $73.66   $73.65   $73.70  
  7 purchase totals = $982.32       $1,061.5818   $1,061.58   $1,061.55   $1,061.50