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	$48.70	8.134%	$52.6613	$52.66	$52.65	$52.70
Purchase #2	$62.80	3.768%	$65.1663	$65.17	$65.15	$65.20
Purchase #3	$36.81	11.831%	$41.165	$41.17	$41.15	$41.20
Purchase #4	$207.89	9.500%	$227.6396	$227.64	$227.65	$227.60
Purchase #5	$35.61	6.216%	$37.8235	$37.82	$37.80	$37.80
Purchase #6	$71.75	10.510%	$79.2909	$79.29	$79.30	$79.30
Purchase #7	$17.89	4.827%	$18.7536	$18.75	$18.75	$18.80
7 purchase totals =	$481.45		$522.5002	$522.50	$522.45	$522.60