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	$43.61	13.761%	$49.6112	$49.61	$49.60	$49.60
Purchase #2	$194.84	11.376%	$217.005	$217.01	$217.00	$217.00
Purchase #3	$239.76	6.512%	$255.3732	$255.37	$255.35	$255.40
Purchase #4	$99.72	4.268%	$103.976	$103.98	$104.00	$104.00
Purchase #5	$115.78	11.793%	$129.4339	$129.43	$129.45	$129.40
Purchase #6	$62.25	5.324%	$65.5642	$65.56	$65.55	$65.60
Purchase #7	$179.40	10.552%	$198.3303	$198.33	$198.35	$198.30
7 purchase totals =	$935.36		$1,019.2938	$1,019.29	$1,019.30	$1,019.30