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	$181.58	13.679%	$206.4183	$206.42	$206.40	$206.40
Purchase #2	$72.91	10.337%	$80.4467	$80.45	$80.45	$80.40
Purchase #3	$196.70	13.795%	$223.8348	$223.83	$223.85	$223.80
Purchase #4	$56.65	6.808%	$60.5067	$60.51	$60.50	$60.50
Purchase #5	$241.54	11.708%	$269.8195	$269.82	$269.80	$269.80
Purchase #6	$153.50	9.220%	$167.6527	$167.65	$167.65	$167.70
Purchase #7	$159.37	4.436%	$166.4397	$166.44	$166.45	$166.40
7 purchase totals =	$1,062.25		$1,175.1184	$1,175.12	$1,175.10	$1,175.00