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 $44.38   10.303%   $48.9525   $48.95   $48.95   $49.00  
  Purchase #2 $98.40   11.110%   $109.3322   $109.33   $109.35   $109.30  
  Purchase #3 $211.76   6.231%   $224.9548   $224.95   $224.95   $225.00  
  Purchase #4 $120.91   4.186%   $125.9713   $125.97   $125.95   $126.00  
  Purchase #5 $161.28   7.463%   $173.3163   $173.32   $173.30   $173.30  
  Purchase #6 $60.83   13.289%   $68.9137   $68.91   $68.90   $68.90  
  Purchase #7 $211.31   10.481%   $233.4574   $233.46   $233.45   $233.50  
  7 purchase totals = $908.87       $984.8982   $984.89   $984.85   $985.00