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	$158.43	9.610%	$173.6551	$173.66	$173.65	$173.70
Purchase #2	$36.61	13.284%	$41.4733	$41.47	$41.45	$41.50
Purchase #3	$145.65	5.102%	$153.0811	$153.08	$153.10	$153.10
Purchase #4	$134.26	6.548%	$143.0513	$143.05	$143.05	$143.10
Purchase #5	$210.33	13.302%	$238.3081	$238.31	$238.30	$238.30
Purchase #6	$127.94	7.179%	$137.1248	$137.12	$137.10	$137.10
Purchase #7	$198.74	7.469%	$213.5839	$213.58	$213.60	$213.60
7 purchase totals =	$1,011.96		$1,100.2776	$1,100.27	$1,100.25	$1,100.40