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	$115.45	10.368%	$127.4199	$127.42	$127.40	$127.40
Purchase #2	$164.98	9.676%	$180.9435	$180.94	$180.95	$180.90
Purchase #3	$137.76	10.840%	$152.6932	$152.69	$152.70	$152.70
Purchase #4	$210.87	9.202%	$230.2743	$230.27	$230.25	$230.30
Purchase #5	$43.79	4.398%	$45.7159	$45.72	$45.70	$45.70
Purchase #6	$40.28	8.171%	$43.5713	$43.57	$43.55	$43.60
Purchase #7	$91.60	11.677%	$102.2961	$102.30	$102.30	$102.30
7 purchase totals =	$804.73		$882.9142	$882.91	$882.85	$882.90