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	$74.70	5.130%	$78.5321	$78.53	$78.55	$78.50
Purchase #2	$107.66	9.670%	$118.0707	$118.07	$118.05	$118.10
Purchase #3	$46.78	3.580%	$48.4547	$48.45	$48.45	$48.50
Purchase #4	$40.77	8.176%	$44.1034	$44.10	$44.10	$44.10
Purchase #5	$217.93	11.752%	$243.5411	$243.54	$243.55	$243.50
Purchase #6	$117.50	8.168%	$127.0974	$127.10	$127.10	$127.10
Purchase #7	$97.35	7.175%	$104.3349	$104.33	$104.35	$104.30
7 purchase totals =	$702.69		$764.1343	$764.12	$764.15	$764.10