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	$211.27	6.326%	$224.6349	$224.63	$224.65	$224.60
Purchase #2	$229.75	12.855%	$259.2844	$259.28	$259.30	$259.30
Purchase #3	$6.61	9.668%	$7.2491	$7.25	$7.25	$7.20
Purchase #4	$9.88	5.572%	$10.4305	$10.43	$10.45	$10.40
Purchase #5	$11.87	10.646%	$13.1337	$13.13	$13.15	$13.10
Purchase #6	$82.93	6.312%	$88.1645	$88.16	$88.15	$88.20
Purchase #7	$89.56	12.315%	$100.5893	$100.59	$100.60	$100.60
7 purchase totals =	$641.87		$703.4864	$703.47	$703.55	$703.40