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 $58.55   5.827%   $61.9617   $61.96   $61.95   $62.00  
  Purchase #2 $176.87   8.195%   $191.3645   $191.36   $191.35   $191.40  
  Purchase #3 $243.89   8.371%   $264.306   $264.31   $264.30   $264.30  
  Purchase #4 $82.36   4.125%   $85.7574   $85.76   $85.75   $85.80  
  Purchase #5 $56.88   10.837%   $63.0441   $63.04   $63.05   $63.00  
  Purchase #6 $148.74   13.372%   $168.6295   $168.63   $168.65   $168.60  
  Purchase #7 $92.70   7.784%   $99.9158   $99.92   $99.90   $99.90  
  7 purchase totals = $859.99       $934.9790   $934.98   $934.95   $935.00