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	$127.45	13.295%	$144.3945	$144.39	$144.40	$144.40
Purchase #2	$165.77	9.371%	$181.3043	$181.30	$181.30	$181.30
Purchase #3	$149.74	13.475%	$169.9175	$169.92	$169.90	$169.90
Purchase #4	$71.27	13.219%	$80.6912	$80.69	$80.70	$80.70
Purchase #5	$146.74	4.255%	$152.9838	$152.98	$153.00	$153.00
Purchase #6	$115.90	9.786%	$127.242	$127.24	$127.25	$127.20
Purchase #7	$97.97	5.281%	$103.1438	$103.14	$103.15	$103.10
7 purchase totals =	$874.84		$959.6771	$959.66	$959.70	$959.60