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 $61.79   11.739%   $69.0435   $69.04   $69.05   $69.00  
  Purchase #2 $244.89   4.181%   $255.1289   $255.13   $255.15   $255.10  
  Purchase #3 $241.69   6.235%   $256.7594   $256.76   $256.75   $256.80  
  Purchase #4 $108.89   11.550%   $121.4668   $121.47   $121.45   $121.50  
  Purchase #5 $176.48   7.536%   $189.7795   $189.78   $189.80   $189.80  
  Purchase #6 $211.31   13.859%   $240.5955   $240.60   $240.60   $240.60  
  Purchase #7 $206.34   13.537%   $234.2722   $234.27   $234.25   $234.30  
  7 purchase totals = $1,251.39       $1,367.0458   $1,367.05   $1,367.05   $1,367.10