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 $69.33   5.421%   $73.0884   $73.09   $73.10   $73.10  
  Purchase #2 $153.66   5.331%   $161.8516   $161.85   $161.85   $161.90  
  Purchase #3 $231.57   3.779%   $240.321   $240.32   $240.30   $240.30  
  Purchase #4 $102.77   6.463%   $109.412   $109.41   $109.40   $109.40  
  Purchase #5 $101.67   11.855%   $113.723   $113.72   $113.70   $113.70  
  Purchase #6 $142.74   9.146%   $155.795   $155.80   $155.80   $155.80  
  Purchase #7 $94.80   7.543%   $101.9508   $101.95   $101.95   $102.00  
  7 purchase totals = $896.54       $956.1418   $956.14   $956.10   $956.20