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 $195.98   11.721%   $218.9508   $218.95   $218.95   $219.00  
  Purchase #2 $64.82   13.455%   $73.5415   $73.54   $73.55   $73.50  
  Purchase #3 $182.42   4.464%   $190.5632   $190.56   $190.55   $190.60  
  Purchase #4 $44.31   8.857%   $48.2345   $48.23   $48.25   $48.20  
  Purchase #5 $165.60   9.228%   $180.8816   $180.88   $180.90   $180.90  
  Purchase #6 $177.64   8.154%   $192.1248   $192.12   $192.10   $192.10  
  Purchase #7 $44.60   9.723%   $48.9365   $48.94   $48.95   $48.90  
  7 purchase totals = $875.37       $953.2329   $953.22   $953.25   $953.20