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	$23.41	6.245%	$24.872	$24.87	$24.85	$24.90
Purchase #2	$54.34	9.212%	$59.3458	$59.35	$59.35	$59.30
Purchase #3	$41.33	4.389%	$43.144	$43.14	$43.15	$43.10
Purchase #4	$201.38	4.361%	$210.1622	$210.16	$210.15	$210.20
Purchase #5	$123.45	7.309%	$132.473	$132.47	$132.45	$132.50
Purchase #6	$62.94	6.179%	$66.8291	$66.83	$66.85	$66.80
Purchase #7	$216.87	10.601%	$239.8604	$239.86	$239.85	$239.90
7 purchase totals =	$723.72		$776.6865	$776.68	$776.65	$776.70