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	$108.58	9.270%	$118.6454	$118.65	$118.65	$118.60
Purchase #2	$158.94	13.534%	$180.4509	$180.45	$180.45	$180.50
Purchase #3	$241.42	5.276%	$254.1573	$254.16	$254.15	$254.20
Purchase #4	$37.65	12.461%	$42.3416	$42.34	$42.35	$42.30
Purchase #5	$143.43	11.640%	$160.1253	$160.13	$160.15	$160.10
Purchase #6	$223.61	6.843%	$238.9116	$238.91	$238.90	$238.90
Purchase #7	$100.28	8.633%	$108.9372	$108.94	$108.95	$108.90
7 purchase totals =	$1,013.91		$1,103.5693	$1,103.58	$1,103.60	$1,103.50