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 $58.89   4.230%   $61.381   $61.38   $61.40   $61.40  
  Purchase #2 $188.49   4.696%   $197.3415   $197.34   $197.35   $197.30  
  Purchase #3 $81.34   7.141%   $87.1485   $87.15   $87.15   $87.10  
  Purchase #4 $221.35   7.497%   $237.9446   $237.94   $237.95   $237.90  
  Purchase #5 $208.29   13.182%   $235.7468   $235.75   $235.75   $235.70  
  Purchase #6 $70.36   12.287%   $79.0051   $79.01   $79.00   $79.00  
  Purchase #7 $244.65   13.344%   $277.2961   $277.30   $277.30   $277.30  
  7 purchase totals = $1,073.37       $1,175.8636   $1,175.87   $1,175.90   $1,175.70