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 $218.48   7.193%   $234.1953   $234.20   $234.20   $234.20  
  Purchase #2 $227.29   4.504%   $237.5271   $237.53   $237.55   $237.50  
  Purchase #3 $101.52   3.183%   $104.7514   $104.75   $104.75   $104.80  
  Purchase #4 $69.41   9.478%   $75.9887   $75.99   $76.00   $76.00  
  Purchase #5 $235.25   9.426%   $257.4247   $257.42   $257.40   $257.40  
  Purchase #6 $222.65   4.106%   $231.792   $231.79   $231.80   $231.80  
  Purchase #7 $196.86   9.201%   $214.9731   $214.97   $214.95   $215.00  
  7 purchase totals = $1,271.46       $1,356.6523   $1,356.65   $1,356.65   $1,356.70