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	$197.39	5.477%	$208.2011	$208.20	$208.20	$208.20
Purchase #2	$146.86	10.436%	$162.1863	$162.19	$162.20	$162.20
Purchase #3	$240.39	6.610%	$256.2798	$256.28	$256.30	$256.30
Purchase #4	$246.56	3.634%	$255.52	$255.52	$255.50	$255.50
Purchase #5	$64.55	9.149%	$70.4557	$70.46	$70.45	$70.50
Purchase #6	$232.68	11.500%	$259.4382	$259.44	$259.45	$259.40
Purchase #7	$20.90	4.542%	$21.8493	$21.85	$21.85	$21.80
7 purchase totals =	$1,149.33		$1,233.9304	$1,233.94	$1,233.95	$1,233.90