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	$66.39	8.867%	$72.2768	$72.28	$72.30	$72.30
Purchase #2	$46.66	12.761%	$52.6143	$52.61	$52.60	$52.60
Purchase #3	$45.26	6.511%	$48.2069	$48.21	$48.20	$48.20
Purchase #4	$241.82	10.709%	$267.7165	$267.72	$267.70	$267.70
Purchase #5	$166.50	12.569%	$187.4274	$187.43	$187.45	$187.40
Purchase #6	$78.32	3.495%	$81.0573	$81.06	$81.05	$81.10
Purchase #7	$172.99	7.471%	$185.9141	$185.91	$185.90	$185.90
7 purchase totals =	$817.94		$895.2133	$895.22	$895.20	$895.20