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	$135.25	7.275%	$145.0894	$145.09	$145.10	$145.10
Purchase #2	$138.28	11.412%	$154.0605	$154.06	$154.05	$154.10
Purchase #3	$123.35	7.289%	$132.341	$132.34	$132.35	$132.30
Purchase #4	$226.89	12.554%	$255.3738	$255.37	$255.35	$255.40
Purchase #5	$97.46	10.419%	$107.6144	$107.61	$107.60	$107.60
Purchase #6	$95.60	4.352%	$99.7605	$99.76	$99.75	$99.80
Purchase #7	$206.78	7.575%	$222.4436	$222.44	$222.45	$222.40
7 purchase totals =	$1,023.61		$1,116.6832	$1,116.67	$1,116.65	$1,116.70