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	$12.89	11.520%	$14.3749	$14.37	$14.35	$14.40
Purchase #2	$145.54	10.405%	$160.6834	$160.68	$160.70	$160.70
Purchase #3	$138.37	12.378%	$155.4974	$155.50	$155.50	$155.50
Purchase #4	$245.72	13.773%	$279.563	$279.56	$279.55	$279.60
Purchase #5	$247.66	12.371%	$278.298	$278.30	$278.30	$278.30
Purchase #6	$102.99	6.409%	$109.5906	$109.59	$109.60	$109.60
Purchase #7	$49.54	10.286%	$54.6357	$54.64	$54.65	$54.60
7 purchase totals =	$942.71		$1,052.6430	$1,052.64	$1,052.65	$1,052.70