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	$137.99	10.128%	$151.9656	$151.97	$151.95	$152.00
Purchase #2	$37.50	10.290%	$41.3588	$41.36	$41.35	$41.40
Purchase #3	$201.99	10.294%	$222.7829	$222.78	$222.80	$222.80
Purchase #4	$112.52	13.367%	$127.5605	$127.56	$127.55	$127.60
Purchase #5	$234.97	12.555%	$264.4705	$264.47	$264.45	$264.50
Purchase #6	$71.27	4.384%	$74.3945	$74.39	$74.40	$74.40
Purchase #7	$172.94	9.167%	$188.7934	$188.79	$188.80	$188.80
7 purchase totals =	$969.18		$1,071.3262	$1,071.32	$1,071.30	$1,071.50