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 $68.59   12.145%   $76.9203   $76.92   $76.90   $76.90  
  Purchase #2 $12.99   10.666%   $14.3755   $14.38   $14.40   $14.40  
  Purchase #3 $20.74   8.734%   $22.5514   $22.55   $22.55   $22.60  
  Purchase #4 $195.62   3.310%   $202.095   $202.10   $202.10   $202.10  
  Purchase #5 $69.58   4.524%   $72.7278   $72.73   $72.75   $72.70  
  Purchase #6 $113.30   5.729%   $119.791   $119.79   $119.80   $119.80  
  Purchase #7 $222.74   13.133%   $251.9924   $251.99   $252.00   $252.00  
  7 purchase totals = $703.56       $760.4534   $760.46   $760.50   $760.50