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 $193.82   6.310%   $206.05   $206.05   $206.05   $206.10  
  Purchase #2 $242.50   8.351%   $262.7512   $262.75   $262.75   $262.80  
  Purchase #3 $95.67   6.188%   $101.5901   $101.59   $101.60   $101.60  
  Purchase #4 $96.50   10.761%   $106.8844   $106.88   $106.90   $106.90  
  Purchase #5 $104.55   11.279%   $116.3422   $116.34   $116.35   $116.30  
  Purchase #6 $41.63   3.842%   $43.2294   $43.23   $43.25   $43.20  
  Purchase #7 $249.64   7.630%   $268.6875   $268.69   $268.70   $268.70  
  7 purchase totals = $1,024.31       $1,105.5348   $1,105.53   $1,105.60   $1,105.60