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 $236.70   7.560%   $254.5945   $254.59   $254.60   $254.60  
  Purchase #2 $89.46   6.220%   $95.0244   $95.02   $95.00   $95.00  
  Purchase #3 $167.42   5.635%   $176.8541   $176.85   $176.85   $176.90  
  Purchase #4 $233.76   6.448%   $248.8328   $248.83   $248.85   $248.80  
  Purchase #5 $126.68   8.298%   $137.1919   $137.19   $137.20   $137.20  
  Purchase #6 $48.29   9.807%   $53.0258   $53.03   $53.05   $53.00  
  Purchase #7 $101.63   5.453%   $107.1719   $107.17   $107.15   $107.20  
  7 purchase totals = $1,003.94       $1,072.6954   $1,072.68   $1,072.70   $1,072.70