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 $61.89   5.366%   $65.211   $65.21   $65.20   $65.20  
  Purchase #2 $119.33   11.776%   $133.3823   $133.38   $133.40   $133.40  
  Purchase #3 $182.47   11.871%   $204.131   $204.13   $204.15   $204.10  
  Purchase #4 $69.41   5.691%   $73.3601   $73.36   $73.35   $73.40  
  Purchase #5 $166.55   6.517%   $177.4041   $177.40   $177.40   $177.40  
  Purchase #6 $5.54   7.295%   $5.9441   $5.94   $5.95   $5.90  
  Purchase #7 $64.36   6.145%   $68.3149   $68.31   $68.30   $68.30  
  7 purchase totals = $669.55       $727.7475   $727.73   $727.75   $727.70