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 $215.36   10.163%   $237.247   $237.25   $237.25   $237.20  
  Purchase #2 $91.94   6.741%   $98.1377   $98.14   $98.15   $98.10  
  Purchase #3 $174.90   13.653%   $198.7791   $198.78   $198.80   $198.80  
  Purchase #4 $249.26   7.836%   $268.792   $268.79   $268.80   $268.80  
  Purchase #5 $199.93   12.326%   $224.5734   $224.57   $224.55   $224.60  
  Purchase #6 $242.62   4.185%   $252.7736   $252.77   $252.75   $252.80  
  Purchase #7 $111.59   8.152%   $120.6868   $120.69   $120.70   $120.70  
  7 purchase totals = $1,285.60       $1,400.9896   $1,400.99   $1,401.00   $1,401.00