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	$158.43	12.636%	$178.4492	$178.45	$178.45	$178.40
Purchase #2	$30.58	7.237%	$32.7931	$32.79	$32.80	$32.80
Purchase #3	$79.38	3.371%	$82.0559	$82.06	$82.05	$82.10
Purchase #4	$107.71	6.614%	$114.8339	$114.83	$114.85	$114.80
Purchase #5	$74.92	5.195%	$78.8121	$78.81	$78.80	$78.80
Purchase #6	$155.78	13.428%	$176.6981	$176.70	$176.70	$176.70
Purchase #7	$47.27	4.155%	$49.2341	$49.23	$49.25	$49.20
7 purchase totals =	$654.07		$712.8764	$712.87	$712.90	$712.80