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	$48.25	11.720%	$53.9049	$53.90	$53.90	$53.90
Purchase #2	$105.28	5.618%	$111.1946	$111.19	$111.20	$111.20
Purchase #3	$42.72	3.245%	$44.1063	$44.11	$44.10	$44.10
Purchase #4	$247.94	7.391%	$266.2652	$266.27	$266.25	$266.30
Purchase #5	$57.63	3.438%	$59.6113	$59.61	$59.60	$59.60
Purchase #6	$195.74	9.596%	$214.5232	$214.52	$214.50	$214.50
Purchase #7	$176.41	6.166%	$187.2874	$187.29	$187.30	$187.30
7 purchase totals =	$873.97		$936.8929	$936.89	$936.85	$936.90