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 $57.79   4.819%   $60.5749   $60.57   $60.55   $60.60  
  Purchase #2 $65.64   8.484%   $71.2089   $71.21   $71.20   $71.20  
  Purchase #3 $175.75   5.349%   $185.1509   $185.15   $185.15   $185.20  
  Purchase #4 $176.75   10.809%   $195.8549   $195.85   $195.85   $195.90  
  Purchase #5 $23.34   13.820%   $26.5656   $26.57   $26.55   $26.60  
  Purchase #6 $214.55   8.261%   $232.274   $232.27   $232.25   $232.30  
  Purchase #7 $247.79   9.870%   $272.2469   $272.25   $272.25   $272.20  
  7 purchase totals = $961.61       $1,043.8761   $1,043.87   $1,043.80   $1,044.00