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	$171.96	13.239%	$194.7258	$194.73	$194.75	$194.70
Purchase #2	$137.86	10.779%	$152.7199	$152.72	$152.70	$152.70
Purchase #3	$57.32	7.291%	$61.4992	$61.50	$61.50	$61.50
Purchase #4	$111.67	5.136%	$117.4054	$117.41	$117.40	$117.40
Purchase #5	$64.57	7.786%	$69.5974	$69.60	$69.60	$69.60
Purchase #6	$37.94	4.607%	$39.6879	$39.69	$39.70	$39.70
Purchase #7	$42.51	4.174%	$44.2844	$44.28	$44.30	$44.30
7 purchase totals =	$623.83		$679.9200	$679.93	$679.95	$679.90