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	$189.89	13.575%	$215.6676	$215.67	$215.65	$215.70
Purchase #2	$165.92	4.287%	$173.033	$173.03	$173.05	$173.00
Purchase #3	$47.72	7.114%	$51.1148	$51.11	$51.10	$51.10
Purchase #4	$73.51	9.568%	$80.5434	$80.54	$80.55	$80.50
Purchase #5	$216.94	12.170%	$243.3416	$243.34	$243.35	$243.30
Purchase #6	$119.90	6.409%	$127.5844	$127.58	$127.60	$127.60
Purchase #7	$205.66	12.697%	$231.7727	$231.77	$231.75	$231.80
7 purchase totals =	$1,019.54		$1,123.0575	$1,123.04	$1,123.05	$1,123.00