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	$155.64	13.282%	$176.3121	$176.31	$176.30	$176.30
Purchase #2	$127.55	11.456%	$142.1621	$142.16	$142.15	$142.20
Purchase #3	$243.47	9.567%	$266.7628	$266.76	$266.75	$266.80
Purchase #4	$51.43	11.321%	$57.2524	$57.25	$57.25	$57.30
Purchase #5	$10.45	10.792%	$11.5778	$11.58	$11.60	$11.60
Purchase #6	$125.47	4.576%	$131.2115	$131.21	$131.20	$131.20
Purchase #7	$213.93	9.420%	$234.0822	$234.08	$234.10	$234.10
7 purchase totals =	$927.94		$1,019.3609	$1,019.35	$1,019.35	$1,019.50