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 $175.36   11.354%   $195.2704   $195.27   $195.25   $195.30  
  Purchase #2 $64.93   11.320%   $72.2801   $72.28   $72.30   $72.30  
  Purchase #3 $159.91   10.385%   $176.5167   $176.52   $176.50   $176.50  
  Purchase #4 $171.76   12.395%   $193.0497   $193.05   $193.05   $193.00  
  Purchase #5 $130.78   12.692%   $147.3786   $147.38   $147.40   $147.40  
  Purchase #6 $155.93   8.696%   $169.4897   $169.49   $169.50   $169.50  
  Purchase #7 $131.88   9.378%   $144.2477   $144.25   $144.25   $144.20  
  7 purchase totals = $990.55       $1,098.2329   $1,098.24   $1,098.25   $1,098.20