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 $62.58   10.722%   $69.2898   $69.29   $69.30   $69.30  
  Purchase #2 $188.25   3.496%   $194.8312   $194.83   $194.85   $194.80  
  Purchase #3 $114.83   3.692%   $119.0695   $119.07   $119.05   $119.10  
  Purchase #4 $170.92   12.141%   $191.6714   $191.67   $191.65   $191.70  
  Purchase #5 $63.36   6.462%   $67.4543   $67.45   $67.45   $67.50  
  Purchase #6 $43.60   12.644%   $49.1128   $49.11   $49.10   $49.10  
  Purchase #7 $215.55   7.742%   $232.2379   $232.24   $232.25   $232.20  
  7 purchase totals = $859.09       $923.6669   $923.66   $923.65   $923.70