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	$159.33	4.445%	$166.4122	$166.41	$166.40	$166.40
Purchase #2	$123.52	12.436%	$138.8809	$138.88	$138.90	$138.90
Purchase #3	$148.43	6.655%	$158.308	$158.31	$158.30	$158.30
Purchase #4	$12.46	8.833%	$13.5606	$13.56	$13.55	$13.60
Purchase #5	$111.29	11.112%	$123.6565	$123.66	$123.65	$123.70
Purchase #6	$190.36	3.462%	$196.9503	$196.95	$196.95	$197.00
Purchase #7	$95.84	5.788%	$101.3872	$101.39	$101.40	$101.40
7 purchase totals =	$841.23		$899.1557	$899.16	$899.15	$899.30