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 $183.44   7.340%   $196.9045   $196.90   $196.90   $196.90  
  Purchase #2 $111.74   6.214%   $118.6835   $118.68   $118.70   $118.70  
  Purchase #3 $115.48   10.486%   $127.5892   $127.59   $127.60   $127.60  
  Purchase #4 $231.52   13.252%   $262.201   $262.20   $262.20   $262.20  
  Purchase #5 $189.54   3.533%   $196.2364   $196.24   $196.25   $196.20  
  Purchase #6 $208.68   13.713%   $237.2963   $237.30   $237.30   $237.30  
  Purchase #7 $156.92   4.298%   $163.6644   $163.66   $163.65   $163.70  
  7 purchase totals = $1,197.32       $1,302.5753   $1,302.57   $1,302.60   $1,302.60