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	$116.84	9.412%	$127.837	$127.84	$127.85	$127.80
Purchase #2	$233.25	6.727%	$248.9407	$248.94	$248.95	$248.90
Purchase #3	$214.76	12.758%	$242.1591	$242.16	$242.15	$242.20
Purchase #4	$12.88	13.397%	$14.6055	$14.61	$14.60	$14.60
Purchase #5	$105.73	7.605%	$113.7708	$113.77	$113.75	$113.80
Purchase #6	$48.81	3.466%	$50.5018	$50.50	$50.50	$50.50
Purchase #7	$212.78	9.248%	$232.4579	$232.46	$232.45	$232.50
7 purchase totals =	$945.05		$1,030.2728	$1,030.28	$1,030.25	$1,030.30