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 $180.75   8.189%   $195.5516   $195.55   $195.55   $195.60  
  Purchase #2 $56.41   6.654%   $60.1635   $60.16   $60.15   $60.20  
  Purchase #3 $70.46   10.523%   $77.8745   $77.87   $77.85   $77.90  
  Purchase #4 $206.52   6.405%   $219.7476   $219.75   $219.75   $219.70  
  Purchase #5 $25.27   6.627%   $26.9446   $26.94   $26.95   $26.90  
  Purchase #6 $104.38   11.734%   $116.6279   $116.63   $116.65   $116.60  
  Purchase #7 $242.60   9.551%   $265.7707   $265.77   $265.75   $265.80  
  7 purchase totals = $886.39       $962.6804   $962.67   $962.65   $962.70