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 $60.50   5.292%   $63.7017   $63.70   $63.70   $63.70  
  Purchase #2 $210.26   11.201%   $233.8112   $233.81   $233.80   $233.80  
  Purchase #3 $154.48   9.344%   $168.9146   $168.91   $168.90   $168.90  
  Purchase #4 $19.75   11.710%   $22.0627   $22.06   $22.05   $22.10  
  Purchase #5 $167.39   5.152%   $176.0139   $176.01   $176.00   $176.00  
  Purchase #6 $221.29   12.831%   $249.6837   $249.68   $249.70   $249.70  
  Purchase #7 $148.50   7.583%   $159.7608   $159.76   $159.75   $159.80  
  7 purchase totals = $982.17       $1,073.9486   $1,073.93   $1,073.90   $1,074.00