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 $118.87   6.228%   $126.2732   $126.27   $126.25   $126.30  
  Purchase #2 $223.96   5.654%   $236.6227   $236.62   $236.60   $236.60  
  Purchase #3 $115.39   6.388%   $122.7611   $122.76   $122.75   $122.80  
  Purchase #4 $205.99   13.289%   $233.364   $233.36   $233.35   $233.40  
  Purchase #5 $79.72   12.357%   $89.571   $89.57   $89.55   $89.60  
  Purchase #6 $214.84   8.252%   $232.5686   $232.57   $232.55   $232.60  
  Purchase #7 $47.69   6.262%   $50.6763   $50.68   $50.70   $50.70  
  7 purchase totals = $1,006.46       $1,091.8369   $1,091.83   $1,091.75   $1,092.00