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	$114.65	11.404%	$127.7247	$127.72	$127.70	$127.70
Purchase #2	$15.70	7.810%	$16.9262	$16.93	$16.95	$16.90
Purchase #3	$128.38	4.766%	$134.4986	$134.50	$134.50	$134.50
Purchase #4	$152.62	7.487%	$164.0467	$164.05	$164.05	$164.00
Purchase #5	$30.29	5.200%	$31.8651	$31.87	$31.85	$31.90
Purchase #6	$30.55	6.340%	$32.4869	$32.49	$32.50	$32.50
Purchase #7	$244.92	4.288%	$255.4222	$255.42	$255.40	$255.40
7 purchase totals =	$717.11		$762.9704	$762.98	$762.95	$762.90