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	$146.29	7.255%	$156.9033	$156.90	$156.90	$156.90
Purchase #2	$183.53	5.307%	$193.2699	$193.27	$193.25	$193.30
Purchase #3	$117.91	7.364%	$126.5929	$126.59	$126.60	$126.60
Purchase #4	$89.69	5.159%	$94.3171	$94.32	$94.30	$94.30
Purchase #5	$229.53	11.213%	$255.2672	$255.27	$255.25	$255.30
Purchase #6	$119.64	6.159%	$127.0086	$127.01	$127.00	$127.00
Purchase #7	$102.94	13.350%	$116.6825	$116.68	$116.70	$116.70
7 purchase totals =	$989.53		$1,070.0415	$1,070.04	$1,070.00	$1,070.10