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 $177.92   13.254%   $201.5015   $201.50   $201.50   $201.50  
  Purchase #2 $66.73   4.307%   $69.6041   $69.60   $69.60   $69.60  
  Purchase #3 $117.95   12.483%   $132.6737   $132.67   $132.65   $132.70  
  Purchase #4 $44.47   8.706%   $48.3416   $48.34   $48.35   $48.30  
  Purchase #5 $191.38   10.285%   $211.0634   $211.06   $211.05   $211.10  
  Purchase #6 $173.26   5.593%   $182.9504   $182.95   $182.95   $183.00  
  Purchase #7 $188.74   13.796%   $214.7786   $214.78   $214.80   $214.80  
  7 purchase totals = $960.45       $1,060.9133   $1,060.90   $1,060.90   $1,061.00