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	$219.42	3.367%	$226.8079	$226.81	$226.80	$226.80
Purchase #2	$127.45	9.219%	$139.1996	$139.20	$139.20	$139.20
Purchase #3	$159.89	13.422%	$181.3504	$181.35	$181.35	$181.40
Purchase #4	$220.98	10.860%	$244.9784	$244.98	$245.00	$245.00
Purchase #5	$158.93	8.399%	$172.2785	$172.28	$172.30	$172.30
Purchase #6	$105.71	10.519%	$116.8296	$116.83	$116.85	$116.80
Purchase #7	$117.66	8.459%	$127.6129	$127.61	$127.60	$127.60
7 purchase totals =	$1,110.04		$1,209.0573	$1,209.06	$1,209.10	$1,209.10