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	$151.75	4.460%	$158.5181	$158.52	$158.50	$158.50
Purchase #2	$211.70	6.708%	$225.9008	$225.90	$225.90	$225.90
Purchase #3	$74.78	6.417%	$79.5786	$79.58	$79.60	$79.60
Purchase #4	$56.91	4.194%	$59.2968	$59.30	$59.30	$59.30
Purchase #5	$242.69	6.408%	$258.2416	$258.24	$258.25	$258.20
Purchase #6	$128.61	12.307%	$144.438	$144.44	$144.45	$144.40
Purchase #7	$239.65	8.239%	$259.3948	$259.39	$259.40	$259.40
7 purchase totals =	$1,106.09		$1,185.3687	$1,185.37	$1,185.40	$1,185.30