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	$81.64	9.200%	$89.1509	$89.15	$89.15	$89.20
Purchase #2	$217.51	11.155%	$241.7732	$241.77	$241.75	$241.80
Purchase #3	$124.58	12.262%	$139.856	$139.86	$139.85	$139.90
Purchase #4	$36.81	6.527%	$39.2126	$39.21	$39.20	$39.20
Purchase #5	$24.32	9.279%	$26.5767	$26.58	$26.60	$26.60
Purchase #6	$102.75	8.773%	$111.7643	$111.76	$111.75	$111.80
Purchase #7	$197.42	4.319%	$205.9466	$205.95	$205.95	$205.90
7 purchase totals =	$785.03		$854.2803	$854.28	$854.25	$854.40