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 $243.43   7.798%   $262.4127   $262.41   $262.40   $262.40  
  Purchase #2 $59.83   8.646%   $65.0029   $65.00   $65.00   $65.00  
  Purchase #3 $10.91   6.736%   $11.6449   $11.64   $11.65   $11.60  
  Purchase #4 $54.39   9.170%   $59.3776   $59.38   $59.40   $59.40  
  Purchase #5 $228.41   4.147%   $237.8822   $237.88   $237.90   $237.90  
  Purchase #6 $208.77   10.814%   $231.3464   $231.35   $231.35   $231.30  
  Purchase #7 $86.36   8.209%   $93.4493   $93.45   $93.45   $93.40  
  7 purchase totals = $892.10       $961.1160   $961.11   $961.15   $961.00