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	$208.33	13.278%	$235.9921	$235.99	$236.00	$236.00
Purchase #2	$44.33	3.272%	$45.7805	$45.78	$45.80	$45.80
Purchase #3	$94.51	4.804%	$99.0503	$99.05	$99.05	$99.10
Purchase #4	$74.71	10.116%	$82.2677	$82.27	$82.25	$82.30
Purchase #5	$173.69	5.663%	$183.5261	$183.53	$183.55	$183.50
Purchase #6	$17.26	8.680%	$18.7582	$18.76	$18.75	$18.80
Purchase #7	$10.82	8.793%	$11.7714	$11.77	$11.75	$11.80
7 purchase totals =	$623.65		$677.1463	$677.15	$677.15	$677.30