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	$153.74	8.690%	$167.1	$167.10	$167.10	$167.10
Purchase #2	$122.49	4.428%	$127.9139	$127.91	$127.90	$127.90
Purchase #3	$145.67	10.535%	$161.0163	$161.02	$161.00	$161.00
Purchase #4	$94.36	5.255%	$99.3186	$99.32	$99.30	$99.30
Purchase #5	$196.29	6.632%	$209.308	$209.31	$209.30	$209.30
Purchase #6	$77.73	4.234%	$81.0211	$81.02	$81.00	$81.00
Purchase #7	$117.51	5.385%	$123.8379	$123.84	$123.85	$123.80
7 purchase totals =	$907.79		$969.5158	$969.52	$969.45	$969.40