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	$158.31	9.500%	$173.3495	$173.35	$173.35	$173.30
Purchase #2	$179.25	10.772%	$198.5588	$198.56	$198.55	$198.60
Purchase #3	$197.81	12.393%	$222.3246	$222.32	$222.30	$222.30
Purchase #4	$123.61	3.389%	$127.7991	$127.80	$127.80	$127.80
Purchase #5	$5.26	4.627%	$5.5034	$5.50	$5.50	$5.50
Purchase #6	$176.96	9.657%	$194.049	$194.05	$194.05	$194.00
Purchase #7	$44.33	5.694%	$46.8542	$46.85	$46.85	$46.90
7 purchase totals =	$885.53		$968.4386	$968.43	$968.40	$968.40