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	$107.29	3.631%	$111.1857	$111.19	$111.20	$111.20
Purchase #2	$194.66	8.124%	$210.4742	$210.47	$210.45	$210.50
Purchase #3	$242.27	11.249%	$269.523	$269.52	$269.50	$269.50
Purchase #4	$205.70	9.570%	$225.3855	$225.39	$225.40	$225.40
Purchase #5	$63.59	10.275%	$70.1239	$70.12	$70.10	$70.10
Purchase #6	$153.61	3.201%	$158.5271	$158.53	$158.55	$158.50
Purchase #7	$247.46	13.644%	$281.2234	$281.22	$281.20	$281.20
7 purchase totals =	$1,214.58		$1,326.4428	$1,326.44	$1,326.40	$1,326.40