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	$195.42	13.852%	$222.4896	$222.49	$222.50	$222.50
Purchase #2	$108.46	13.618%	$123.2301	$123.23	$123.25	$123.20
Purchase #3	$118.88	12.224%	$133.4119	$133.41	$133.40	$133.40
Purchase #4	$136.55	10.864%	$151.3848	$151.38	$151.40	$151.40
Purchase #5	$7.81	11.365%	$8.6976	$8.70	$8.70	$8.70
Purchase #6	$12.63	9.847%	$13.8737	$13.87	$13.85	$13.90
Purchase #7	$42.50	6.262%	$45.1614	$45.16	$45.15	$45.20
7 purchase totals =	$622.25		$698.2491	$698.24	$698.25	$698.30