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 $68.87   10.776%   $76.2914   $76.29   $76.30   $76.30  
  Purchase #2 $59.71   3.367%   $61.7204   $61.72   $61.70   $61.70  
  Purchase #3 $150.61   10.428%   $166.3156   $166.32   $166.30   $166.30  
  Purchase #4 $156.76   8.407%   $169.9388   $169.94   $169.95   $169.90  
  Purchase #5 $219.78   12.421%   $247.0789   $247.08   $247.10   $247.10  
  Purchase #6 $44.62   13.371%   $50.5861   $50.59   $50.60   $50.60  
  Purchase #7 $115.60   7.289%   $124.0261   $124.03   $124.05   $124.00  
  7 purchase totals = $815.95       $895.9573   $895.97   $896.00   $895.90