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	$71.52	9.437%	$78.2693	$78.27	$78.25	$78.30
Purchase #2	$32.30	4.847%	$33.8656	$33.87	$33.85	$33.90
Purchase #3	$191.86	7.298%	$205.8619	$205.86	$205.85	$205.90
Purchase #4	$217.72	5.837%	$230.4283	$230.43	$230.45	$230.40
Purchase #5	$212.97	8.213%	$230.4612	$230.46	$230.45	$230.50
Purchase #6	$124.60	6.520%	$132.7239	$132.72	$132.70	$132.70
Purchase #7	$162.51	10.579%	$179.7019	$179.70	$179.70	$179.70
7 purchase totals =	$1,013.48		$1,091.3121	$1,091.31	$1,091.25	$1,091.40