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 $91.87   5.509%   $96.9311   $96.93   $96.95   $96.90  
  Purchase #2 $174.54   8.735%   $189.7861   $189.79   $189.80   $189.80  
  Purchase #3 $29.38   3.229%   $30.3287   $30.33   $30.35   $30.30  
  Purchase #4 $188.40   5.424%   $198.6188   $198.62   $198.60   $198.60  
  Purchase #5 $55.56   8.480%   $60.2715   $60.27   $60.25   $60.30  
  Purchase #6 $41.25   7.322%   $44.2703   $44.27   $44.25   $44.30  
  Purchase #7 $213.95   6.253%   $227.3283   $227.33   $227.35   $227.30  
  7 purchase totals = $794.95       $847.5348   $847.54   $847.55   $847.50