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	$65.26	4.103%	$67.9376	$67.94	$67.95	$67.90
Purchase #2	$59.44	5.319%	$62.6016	$62.60	$62.60	$62.60
Purchase #3	$67.77	12.185%	$76.0278	$76.03	$76.05	$76.00
Purchase #4	$62.50	4.511%	$65.3194	$65.32	$65.30	$65.30
Purchase #5	$221.77	10.113%	$244.1976	$244.20	$244.20	$244.20
Purchase #6	$135.39	6.670%	$144.4205	$144.42	$144.40	$144.40
Purchase #7	$26.32	3.692%	$27.2917	$27.29	$27.30	$27.30
7 purchase totals =	$638.45		$687.7962	$687.80	$687.80	$687.70