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 $44.80   3.171%   $46.2206   $46.22   $46.20   $46.20  
  Purchase #2 $190.82   5.656%   $201.6128   $201.61   $201.60   $201.60  
  Purchase #3 $66.63   5.516%   $70.3053   $70.31   $70.30   $70.30  
  Purchase #4 $184.53   13.127%   $208.7533   $208.75   $208.75   $208.80  
  Purchase #5 $87.90   11.292%   $97.8257   $97.83   $97.85   $97.80  
  Purchase #6 $161.91   8.620%   $175.8666   $175.87   $175.85   $175.90  
  Purchase #7 $148.64   8.659%   $161.5107   $161.51   $161.50   $161.50  
  7 purchase totals = $885.23       $962.0950   $962.10   $962.05   $962.10