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 $214.95   3.559%   $222.6001   $222.60   $222.60   $222.60  
  Purchase #2 $17.83   6.534%   $18.995   $19.00   $19.00   $19.00  
  Purchase #3 $6.73   12.182%   $7.5498   $7.55   $7.55   $7.50  
  Purchase #4 $167.91   3.177%   $173.2445   $173.24   $173.25   $173.20  
  Purchase #5 $248.62   3.310%   $256.8493   $256.85   $256.85   $256.80  
  Purchase #6 $68.33   10.301%   $75.3687   $75.37   $75.35   $75.40  
  Purchase #7 $93.77   12.760%   $105.7351   $105.74   $105.75   $105.70  
  7 purchase totals = $818.14       $860.3425   $860.35   $860.35   $860.20