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	$166.88	7.608%	$179.5762	$179.58	$179.60	$179.60
Purchase #2	$217.34	12.709%	$244.9617	$244.96	$244.95	$245.00
Purchase #3	$39.86	6.712%	$42.5354	$42.54	$42.55	$42.50
Purchase #4	$134.42	10.226%	$148.1658	$148.17	$148.15	$148.20
Purchase #5	$149.75	5.714%	$158.3067	$158.31	$158.30	$158.30
Purchase #6	$49.68	7.443%	$53.3777	$53.38	$53.40	$53.40
Purchase #7	$237.93	4.131%	$247.7589	$247.76	$247.75	$247.80
7 purchase totals =	$995.86		$1,074.6824	$1,074.70	$1,074.70	$1,074.80