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	$132.65	13.743%	$150.8801	$150.88	$150.90	$150.90
Purchase #2	$40.61	6.621%	$43.2988	$43.30	$43.30	$43.30
Purchase #3	$175.25	3.289%	$181.014	$181.01	$181.00	$181.00
Purchase #4	$114.80	11.340%	$127.8183	$127.82	$127.80	$127.80
Purchase #5	$246.80	11.286%	$274.6538	$274.65	$274.65	$274.70
Purchase #6	$81.78	13.338%	$92.6878	$92.69	$92.70	$92.70
Purchase #7	$216.80	6.354%	$230.5755	$230.58	$230.60	$230.60
7 purchase totals =	$1,008.69		$1,100.9283	$1,100.93	$1,100.95	$1,101.00