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	$216.58	5.589%	$228.6847	$228.68	$228.70	$228.70
Purchase #2	$48.28	7.405%	$51.8551	$51.86	$51.85	$51.90
Purchase #3	$51.30	10.660%	$56.7686	$56.77	$56.75	$56.80
Purchase #4	$100.51	9.352%	$109.9097	$109.91	$109.90	$109.90
Purchase #5	$143.89	3.390%	$148.7679	$148.77	$148.75	$148.80
Purchase #6	$247.67	9.265%	$270.6166	$270.62	$270.60	$270.60
Purchase #7	$38.50	6.107%	$40.8512	$40.85	$40.85	$40.90
7 purchase totals =	$846.73		$907.4538	$907.46	$907.40	$907.60