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	$46.46	4.541%	$48.5697	$48.57	$48.55	$48.60
Purchase #2	$102.69	8.626%	$111.548	$111.55	$111.55	$111.50
Purchase #3	$142.40	5.863%	$150.7489	$150.75	$150.75	$150.70
Purchase #4	$28.99	6.286%	$30.8123	$30.81	$30.80	$30.80
Purchase #5	$65.27	12.335%	$73.3211	$73.32	$73.30	$73.30
Purchase #6	$172.68	7.245%	$185.1907	$185.19	$185.20	$185.20
Purchase #7	$56.90	4.170%	$59.2727	$59.27	$59.25	$59.30
7 purchase totals =	$615.39		$659.4634	$659.46	$659.40	$659.40