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	$159.83	8.521%	$173.4491	$173.45	$173.45	$173.40
Purchase #2	$18.65	6.651%	$19.8904	$19.89	$19.90	$19.90
Purchase #3	$216.47	3.856%	$224.8171	$224.82	$224.80	$224.80
Purchase #4	$234.48	4.178%	$244.2766	$244.28	$244.30	$244.30
Purchase #5	$179.54	11.721%	$200.5839	$200.58	$200.60	$200.60
Purchase #6	$146.27	6.543%	$155.8404	$155.84	$155.85	$155.80
Purchase #7	$123.41	12.701%	$139.0843	$139.08	$139.10	$139.10
7 purchase totals =	$1,078.65		$1,157.9418	$1,157.94	$1,158.00	$1,157.90