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 $106.97   6.616%   $114.0471   $114.05   $114.05   $114.00  
  Purchase #2 $151.82   13.217%   $171.886   $171.89   $171.90   $171.90  
  Purchase #3 $39.97   4.300%   $41.6887   $41.69   $41.70   $41.70  
  Purchase #4 $186.94   3.120%   $192.7725   $192.77   $192.75   $192.80  
  Purchase #5 $148.28   11.383%   $165.1587   $165.16   $165.15   $165.20  
  Purchase #6 $197.66   4.473%   $206.5013   $206.50   $206.50   $206.50  
  Purchase #7 $246.98   8.477%   $267.9165   $267.92   $267.90   $267.90  
  7 purchase totals = $1,078.62       $1,159.9708   $1,159.98   $1,159.95   $1,160.00