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	$110.44	12.137%	$123.8441	$123.84	$123.85	$123.80
Purchase #2	$102.58	8.270%	$111.0634	$111.06	$111.05	$111.10
Purchase #3	$13.99	3.338%	$14.457	$14.46	$14.45	$14.50
Purchase #4	$235.69	6.565%	$251.163	$251.16	$251.15	$251.20
Purchase #5	$140.26	3.703%	$145.4538	$145.45	$145.45	$145.50
Purchase #6	$54.88	8.645%	$59.6244	$59.62	$59.60	$59.60
Purchase #7	$110.72	5.847%	$117.1938	$117.19	$117.20	$117.20
7 purchase totals =	$768.56		$822.7995	$822.78	$822.75	$822.90