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	$106.47	8.549%	$115.5721	$115.57	$115.55	$115.60
Purchase #2	$26.77	10.554%	$29.5953	$29.60	$29.60	$29.60
Purchase #3	$108.83	8.545%	$118.1295	$118.13	$118.15	$118.10
Purchase #4	$207.61	7.619%	$223.4278	$223.43	$223.45	$223.40
Purchase #5	$100.72	6.389%	$107.155	$107.16	$107.15	$107.20
Purchase #6	$89.84	11.167%	$99.8724	$99.87	$99.85	$99.90
Purchase #7	$36.40	4.729%	$38.1214	$38.12	$38.10	$38.10
7 purchase totals =	$676.64		$731.8735	$731.88	$731.85	$731.90