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 $215.37   5.376%   $226.9483   $226.95   $226.95   $226.90  
  Purchase #2 $84.38   13.724%   $95.9603   $95.96   $95.95   $96.00  
  Purchase #3 $51.69   6.795%   $55.2023   $55.20   $55.20   $55.20  
  Purchase #4 $230.77   10.454%   $254.8947   $254.89   $254.90   $254.90  
  Purchase #5 $176.96   10.136%   $194.8967   $194.90   $194.90   $194.90  
  Purchase #6 $208.99   10.433%   $230.7939   $230.79   $230.80   $230.80  
  Purchase #7 $53.46   10.468%   $59.0562   $59.06   $59.05   $59.10  
  7 purchase totals = $1,021.62       $1,117.7524   $1,117.75   $1,117.75   $1,117.80