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	$107.89	8.573%	$117.1394	$117.14	$117.15	$117.10
Purchase #2	$14.84	13.653%	$16.8661	$16.87	$16.85	$16.90
Purchase #3	$183.62	7.739%	$197.8304	$197.83	$197.85	$197.80
Purchase #4	$29.43	11.690%	$32.8704	$32.87	$32.85	$32.90
Purchase #5	$37.49	13.147%	$42.4188	$42.42	$42.40	$42.40
Purchase #6	$92.68	13.409%	$105.1075	$105.11	$105.10	$105.10
Purchase #7	$127.50	11.404%	$142.0401	$142.04	$142.05	$142.00
7 purchase totals =	$593.45		$654.2727	$654.28	$654.25	$654.20