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	$97.83	11.526%	$109.1059	$109.11	$109.10	$109.10
Purchase #2	$142.40	5.391%	$150.0768	$150.08	$150.10	$150.10
Purchase #3	$14.31	4.541%	$14.9598	$14.96	$14.95	$15.00
Purchase #4	$120.93	7.412%	$129.8933	$129.89	$129.90	$129.90
Purchase #5	$49.31	10.159%	$54.3194	$54.32	$54.30	$54.30
Purchase #6	$34.51	10.671%	$38.1926	$38.19	$38.20	$38.20
Purchase #7	$166.51	4.201%	$173.5051	$173.51	$173.50	$173.50
7 purchase totals =	$625.80		$670.0529	$670.06	$670.05	$670.10