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	$219.29	7.874%	$236.5569	$236.56	$236.55	$236.60
Purchase #2	$229.72	6.448%	$244.5323	$244.53	$244.55	$244.50
Purchase #3	$204.38	8.716%	$222.1938	$222.19	$222.20	$222.20
Purchase #4	$80.72	6.133%	$85.6706	$85.67	$85.65	$85.70
Purchase #5	$155.73	12.820%	$175.6946	$175.69	$175.70	$175.70
Purchase #6	$158.85	11.183%	$176.6142	$176.61	$176.60	$176.60
Purchase #7	$80.43	10.739%	$89.0674	$89.07	$89.05	$89.10
7 purchase totals =	$1,129.12		$1,230.3298	$1,230.32	$1,230.30	$1,230.40