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	$167.75	3.364%	$173.3931	$173.39	$173.40	$173.40
Purchase #2	$247.46	13.420%	$280.6691	$280.67	$280.65	$280.70
Purchase #3	$221.92	13.219%	$251.2556	$251.26	$251.25	$251.30
Purchase #4	$11.52	6.814%	$12.305	$12.31	$12.30	$12.30
Purchase #5	$49.45	4.138%	$51.4962	$51.50	$51.50	$51.50
Purchase #6	$53.69	4.190%	$55.9396	$55.94	$55.95	$55.90
Purchase #7	$219.45	13.256%	$248.5403	$248.54	$248.55	$248.50
7 purchase totals =	$971.24		$1,073.5989	$1,073.61	$1,073.60	$1,073.60