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 $193.51   6.615%   $206.3107   $206.31   $206.30   $206.30  
  Purchase #2 $246.99   8.280%   $267.4408   $267.44   $267.45   $267.40  
  Purchase #3 $219.37   13.172%   $248.2654   $248.27   $248.25   $248.30  
  Purchase #4 $146.32   13.718%   $166.3922   $166.39   $166.40   $166.40  
  Purchase #5 $141.98   7.114%   $152.0805   $152.08   $152.10   $152.10  
  Purchase #6 $176.73   8.139%   $191.1141   $191.11   $191.10   $191.10  
  Purchase #7 $232.30   7.758%   $250.3218   $250.32   $250.30   $250.30  
  7 purchase totals = $1,357.20       $1,481.9255   $1,481.92   $1,481.90   $1,481.90