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 $73.68   3.775%   $76.4614   $76.46   $76.45   $76.50  
  Purchase #2 $190.42   13.313%   $215.7706   $215.77   $215.75   $215.80  
  Purchase #3 $67.36   6.372%   $71.6522   $71.65   $71.65   $71.70  
  Purchase #4 $169.66   10.361%   $187.2385   $187.24   $187.25   $187.20  
  Purchase #5 $159.36   4.723%   $166.8866   $166.89   $166.90   $166.90  
  Purchase #6 $206.58   5.804%   $218.5699   $218.57   $218.55   $218.60  
  Purchase #7 $165.88   3.149%   $171.1036   $171.10   $171.10   $171.10  
  7 purchase totals = $1,032.94       $1,107.6828   $1,107.68   $1,107.65   $1,107.80