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 $211.26   12.356%   $237.3633   $237.36   $237.35   $237.40  
  Purchase #2 $168.95   4.531%   $176.6051   $176.61   $176.60   $176.60  
  Purchase #3 $156.40   10.705%   $173.1426   $173.14   $173.15   $173.10  
  Purchase #4 $146.80   3.697%   $152.2272   $152.23   $152.25   $152.20  
  Purchase #5 $161.69   8.588%   $175.5759   $175.58   $175.60   $175.60  
  Purchase #6 $184.64   7.364%   $198.2369   $198.24   $198.25   $198.20  
  Purchase #7 $167.41   10.772%   $185.4434   $185.44   $185.45   $185.40  
  7 purchase totals = $1,197.15       $1,298.5944   $1,298.60   $1,298.65   $1,298.50