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	$152.74	6.144%	$162.1243	$162.12	$162.10	$162.10
Purchase #2	$105.31	5.466%	$111.0662	$111.07	$111.05	$111.10
Purchase #3	$141.27	6.615%	$150.615	$150.62	$150.60	$150.60
Purchase #4	$127.42	6.745%	$136.0145	$136.01	$136.00	$136.00
Purchase #5	$160.75	12.670%	$181.117	$181.12	$181.10	$181.10
Purchase #6	$109.49	8.478%	$118.7726	$118.77	$118.75	$118.80
Purchase #7	$88.88	12.772%	$100.2318	$100.23	$100.25	$100.20
7 purchase totals =	$885.86		$959.9414	$959.94	$959.85	$959.90