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	$180.26	13.240%	$204.1264	$204.13	$204.15	$204.10
Purchase #2	$142.70	7.276%	$153.0829	$153.08	$153.10	$153.10
Purchase #3	$38.83	10.151%	$42.7716	$42.77	$42.75	$42.80
Purchase #4	$44.68	3.313%	$46.1602	$46.16	$46.15	$46.20
Purchase #5	$39.97	13.617%	$45.4127	$45.41	$45.40	$45.40
Purchase #6	$32.88	10.466%	$36.3212	$36.32	$36.30	$36.30
Purchase #7	$233.78	10.587%	$258.5303	$258.53	$258.55	$258.50
7 purchase totals =	$713.10		$786.4053	$786.40	$786.40	$786.40