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	$149.31	10.583%	$165.1115	$165.11	$165.10	$165.10
Purchase #2	$173.27	12.254%	$194.5025	$194.50	$194.50	$194.50
Purchase #3	$248.51	4.613%	$259.9738	$259.97	$259.95	$260.00
Purchase #4	$176.84	6.503%	$188.3399	$188.34	$188.35	$188.30
Purchase #5	$78.35	6.503%	$83.4451	$83.45	$83.45	$83.40
Purchase #6	$99.49	12.495%	$111.9213	$111.92	$111.90	$111.90
Purchase #7	$133.78	7.128%	$143.3158	$143.32	$143.30	$143.30
7 purchase totals =	$1,059.55		$1,146.6099	$1,146.61	$1,146.55	$1,146.50