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	$161.52	7.211%	$173.1672	$173.17	$173.15	$173.20
Purchase #2	$158.63	12.359%	$178.2351	$178.24	$178.25	$178.20
Purchase #3	$104.75	9.336%	$114.5295	$114.53	$114.55	$114.50
Purchase #4	$127.84	5.122%	$134.388	$134.39	$134.40	$134.40
Purchase #5	$98.70	6.719%	$105.3317	$105.33	$105.35	$105.30
Purchase #6	$210.67	3.654%	$218.3679	$218.37	$218.35	$218.40
Purchase #7	$137.69	6.386%	$146.4829	$146.48	$146.50	$146.50
7 purchase totals =	$999.80		$1,070.5023	$1,070.51	$1,070.55	$1,070.50