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 $44.78   8.582%   $48.623   $48.62   $48.60   $48.60  
  Purchase #2 $175.83   4.257%   $183.3151   $183.32   $183.30   $183.30  
  Purchase #3 $72.48   6.505%   $77.1948   $77.19   $77.20   $77.20  
  Purchase #4 $185.65   11.320%   $206.6656   $206.67   $206.65   $206.70  
  Purchase #5 $15.80   3.161%   $16.2994   $16.30   $16.30   $16.30  
  Purchase #6 $30.61   11.841%   $34.2345   $34.23   $34.25   $34.20  
  Purchase #7 $162.56   10.759%   $180.0498   $180.05   $180.05   $180.00  
  7 purchase totals = $687.71       $746.3822   $746.38   $746.35   $746.30