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	$47.78	13.156%	$54.0659	$54.07	$54.05	$54.10
Purchase #2	$227.64	7.582%	$244.8997	$244.90	$244.90	$244.90
Purchase #3	$93.31	6.552%	$99.4237	$99.42	$99.40	$99.40
Purchase #4	$140.86	12.716%	$158.7718	$158.77	$158.75	$158.80
Purchase #5	$41.99	8.453%	$45.5394	$45.54	$45.55	$45.50
Purchase #6	$72.40	4.553%	$75.6964	$75.70	$75.70	$75.70
Purchase #7	$46.42	3.466%	$48.0289	$48.03	$48.05	$48.00
7 purchase totals =	$670.40		$726.4258	$726.43	$726.40	$726.40