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 $55.27   11.585%   $61.673   $61.67   $61.65   $61.70  
  Purchase #2 $163.50   10.497%   $180.6626   $180.66   $180.65   $180.70  
  Purchase #3 $188.97   9.385%   $206.7048   $206.70   $206.70   $206.70  
  Purchase #4 $238.87   8.632%   $259.4893   $259.49   $259.50   $259.50  
  Purchase #5 $119.33   4.257%   $124.4099   $124.41   $124.40   $124.40  
  Purchase #6 $151.60   8.264%   $164.1282   $164.13   $164.15   $164.10  
  Purchase #7 $221.54   6.483%   $235.9024   $235.90   $235.90   $235.90  
  7 purchase totals = $1,139.08       $1,232.9702   $1,232.96   $1,232.95   $1,233.00