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 $48.63   12.436%   $54.6776   $54.68   $54.70   $54.70  
  Purchase #2 $217.74   4.143%   $226.761   $226.76   $226.75   $226.80  
  Purchase #3 $238.26   11.368%   $265.3454   $265.35   $265.35   $265.30  
  Purchase #4 $231.68   4.255%   $241.538   $241.54   $241.55   $241.50  
  Purchase #5 $46.80   7.308%   $50.2201   $50.22   $50.20   $50.20  
  Purchase #6 $202.63   5.460%   $213.6936   $213.69   $213.70   $213.70  
  Purchase #7 $67.69   6.367%   $71.9998   $72.00   $72.00   $72.00  
  7 purchase totals = $1,053.43       $1,124.2355   $1,124.24   $1,124.25   $1,124.20