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	$151.60	10.605%	$167.6772	$167.68	$167.70	$167.70
Purchase #2	$39.64	5.651%	$41.8801	$41.88	$41.90	$41.90
Purchase #3	$180.83	13.795%	$205.7755	$205.78	$205.80	$205.80
Purchase #4	$6.60	13.873%	$7.5156	$7.52	$7.50	$7.50
Purchase #5	$140.42	12.111%	$157.4263	$157.43	$157.45	$157.40
Purchase #6	$37.56	7.275%	$40.2925	$40.29	$40.30	$40.30
Purchase #7	$49.55	7.753%	$53.3916	$53.39	$53.40	$53.40
7 purchase totals =	$606.20		$673.9588	$673.97	$674.05	$674.00