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 $242.94   3.828%   $252.2397   $252.24   $252.25   $252.20  
  Purchase #2 $206.42   13.179%   $233.6241   $233.62   $233.60   $233.60  
  Purchase #3 $231.68   8.436%   $251.2245   $251.22   $251.20   $251.20  
  Purchase #4 $24.81   5.664%   $26.2152   $26.22   $26.20   $26.20  
  Purchase #5 $104.98   13.757%   $119.4221   $119.42   $119.40   $119.40  
  Purchase #6 $63.87   6.128%   $67.784   $67.78   $67.80   $67.80  
  Purchase #7 $162.65   9.312%   $177.796   $177.80   $177.80   $177.80  
  7 purchase totals = $1,037.35       $1,128.3056   $1,128.30   $1,128.25   $1,128.20