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 $205.82   8.674%   $223.6728   $223.67   $223.65   $223.70  
  Purchase #2 $160.79   5.343%   $169.381   $169.38   $169.40   $169.40  
  Purchase #3 $132.25   13.831%   $150.5415   $150.54   $150.55   $150.50  
  Purchase #4 $93.96   5.309%   $98.9483   $98.95   $98.95   $98.90  
  Purchase #5 $209.97   8.498%   $227.8133   $227.81   $227.80   $227.80  
  Purchase #6 $36.91   10.783%   $40.89   $40.89   $40.90   $40.90  
  Purchase #7 $209.70   5.291%   $220.7952   $220.80   $220.80   $220.80  
  7 purchase totals = $1,049.40       $1,132.0421   $1,132.04   $1,132.05   $1,132.00