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 $196.48   6.559%   $209.3671   $209.37   $209.35   $209.40  
  Purchase #2 $208.59   6.796%   $222.7658   $222.77   $222.75   $222.80  
  Purchase #3 $35.92   8.687%   $39.0404   $39.04   $39.05   $39.00  
  Purchase #4 $246.82   8.455%   $267.6886   $267.69   $267.70   $267.70  
  Purchase #5 $48.48   6.510%   $51.636   $51.64   $51.65   $51.60  
  Purchase #6 $91.93   10.844%   $101.8989   $101.90   $101.90   $101.90  
  Purchase #7 $193.26   10.873%   $214.2732   $214.27   $214.25   $214.30  
  7 purchase totals = $1,021.48       $1,106.6700   $1,106.68   $1,106.65   $1,106.70