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	$182.69	12.423%	$205.3856	$205.39	$205.40	$205.40
Purchase #2	$71.56	10.420%	$79.0166	$79.02	$79.00	$79.00
Purchase #3	$40.29	6.281%	$42.8206	$42.82	$42.80	$42.80
Purchase #4	$37.78	5.615%	$39.9013	$39.90	$39.90	$39.90
Purchase #5	$33.37	3.755%	$34.623	$34.62	$34.60	$34.60
Purchase #6	$121.88	4.258%	$127.0697	$127.07	$127.05	$127.10
Purchase #7	$200.67	11.488%	$223.723	$223.72	$223.70	$223.70
7 purchase totals =	$688.24		$752.5398	$752.54	$752.45	$752.50