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 $86.67   9.598%   $94.9886   $94.99   $95.00   $95.00  
  Purchase #2 $56.83   5.345%   $59.8676   $59.87   $59.85   $59.90  
  Purchase #3 $116.68   9.348%   $127.5872   $127.59   $127.60   $127.60  
  Purchase #4 $187.87   3.584%   $194.6033   $194.60   $194.60   $194.60  
  Purchase #5 $165.47   7.382%   $177.685   $177.69   $177.70   $177.70  
  Purchase #6 $226.82   4.466%   $236.9498   $236.95   $236.95   $236.90  
  Purchase #7 $118.83   11.426%   $132.4075   $132.41   $132.40   $132.40  
  7 purchase totals = $959.17       $1,024.0890   $1,024.10   $1,024.10   $1,024.10