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	$148.27	13.680%	$168.5533	$168.55	$168.55	$168.60
Purchase #2	$99.32	11.861%	$111.1003	$111.10	$111.10	$111.10
Purchase #3	$111.49	3.622%	$115.5282	$115.53	$115.55	$115.50
Purchase #4	$245.94	12.697%	$277.167	$277.17	$277.15	$277.20
Purchase #5	$229.70	13.371%	$260.4132	$260.41	$260.40	$260.40
Purchase #6	$142.47	9.264%	$155.6684	$155.67	$155.65	$155.70
Purchase #7	$156.27	6.657%	$166.6729	$166.67	$166.65	$166.70
7 purchase totals =	$1,133.46		$1,255.1033	$1,255.10	$1,255.05	$1,255.20