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	$12.56	13.761%	$14.2884	$14.29	$14.30	$14.30
Purchase #2	$204.46	4.765%	$214.2025	$214.20	$214.20	$214.20
Purchase #3	$57.73	3.516%	$59.7598	$59.76	$59.75	$59.80
Purchase #4	$155.88	11.784%	$174.2489	$174.25	$174.25	$174.20
Purchase #5	$153.37	4.208%	$159.8238	$159.82	$159.80	$159.80
Purchase #6	$53.92	10.567%	$59.6177	$59.62	$59.60	$59.60
Purchase #7	$60.54	7.506%	$65.0841	$65.08	$65.10	$65.10
7 purchase totals =	$698.46		$747.0252	$747.02	$747.00	$747.00