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	$160.98	5.405%	$169.681	$169.68	$169.70	$169.70
Purchase #2	$143.98	5.476%	$151.8643	$151.86	$151.85	$151.90
Purchase #3	$220.51	12.301%	$247.6349	$247.63	$247.65	$247.60
Purchase #4	$52.27	10.745%	$57.8864	$57.89	$57.90	$57.90
Purchase #5	$245.80	13.109%	$278.0219	$278.02	$278.00	$278.00
Purchase #6	$13.75	12.246%	$15.4338	$15.43	$15.45	$15.40
Purchase #7	$146.33	11.114%	$162.5931	$162.59	$162.60	$162.60
7 purchase totals =	$983.62		$1,083.1154	$1,083.10	$1,083.15	$1,083.10