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	$168.29	3.389%	$173.9933	$173.99	$174.00	$174.00
Purchase #2	$125.72	6.869%	$134.3557	$134.36	$134.35	$134.40
Purchase #3	$221.28	13.652%	$251.4891	$251.49	$251.50	$251.50
Purchase #4	$159.61	3.593%	$165.3448	$165.34	$165.35	$165.30
Purchase #5	$72.78	8.635%	$79.0646	$79.06	$79.05	$79.10
Purchase #6	$214.69	3.618%	$222.4575	$222.46	$222.45	$222.50
Purchase #7	$170.40	11.580%	$190.1323	$190.13	$190.15	$190.10
7 purchase totals =	$1,132.77		$1,216.8373	$1,216.83	$1,216.85	$1,216.90