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 $67.60   10.397%   $74.6284   $74.63   $74.65   $74.60  
  Purchase #2 $248.61   8.539%   $269.8388   $269.84   $269.85   $269.80  
  Purchase #3 $49.83   8.771%   $54.2006   $54.20   $54.20   $54.20  
  Purchase #4 $228.90   11.690%   $255.6584   $255.66   $255.65   $255.70  
  Purchase #5 $122.86   5.244%   $129.3028   $129.30   $129.30   $129.30  
  Purchase #6 $187.55   11.721%   $209.5327   $209.53   $209.55   $209.50  
  Purchase #7 $63.82   10.581%   $70.5728   $70.57   $70.55   $70.60  
  7 purchase totals = $969.17       $1,063.7345   $1,063.73   $1,063.75   $1,063.70