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	$226.54	9.152%	$247.2729	$247.27	$247.25	$247.30
Purchase #2	$129.49	10.670%	$143.3066	$143.31	$143.30	$143.30
Purchase #3	$211.95	5.150%	$222.8654	$222.87	$222.85	$222.90
Purchase #4	$155.78	10.632%	$172.3425	$172.34	$172.35	$172.30
Purchase #5	$76.98	5.789%	$81.4364	$81.44	$81.45	$81.40
Purchase #6	$184.56	4.490%	$192.8467	$192.85	$192.85	$192.80
Purchase #7	$159.99	11.410%	$178.2449	$178.24	$178.25	$178.20
7 purchase totals =	$1,145.29		$1,238.3154	$1,238.32	$1,238.30	$1,238.20