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	$207.40	7.408%	$222.7642	$222.76	$222.75	$222.80
Purchase #2	$38.87	10.479%	$42.9432	$42.94	$42.95	$42.90
Purchase #3	$103.61	7.444%	$111.3227	$111.32	$111.30	$111.30
Purchase #4	$45.25	10.849%	$50.1592	$50.16	$50.15	$50.20
Purchase #5	$129.94	4.428%	$135.6937	$135.69	$135.70	$135.70
Purchase #6	$105.46	13.548%	$119.7477	$119.75	$119.75	$119.70
Purchase #7	$234.27	10.255%	$258.2944	$258.29	$258.30	$258.30
7 purchase totals =	$864.80		$940.9251	$940.91	$940.90	$940.90