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	$11.74	5.619%	$12.3997	$12.40	$12.40	$12.40
Purchase #2	$54.87	9.643%	$60.1611	$60.16	$60.15	$60.20
Purchase #3	$119.35	3.847%	$123.9414	$123.94	$123.95	$123.90
Purchase #4	$245.89	13.527%	$279.1515	$279.15	$279.15	$279.20
Purchase #5	$245.92	7.659%	$264.755	$264.76	$264.75	$264.80
Purchase #6	$166.72	5.532%	$175.943	$175.94	$175.95	$175.90
Purchase #7	$114.85	4.393%	$119.8954	$119.90	$119.90	$119.90
7 purchase totals =	$959.34		$1,036.2471	$1,036.25	$1,036.25	$1,036.30