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	$67.42	11.818%	$75.3877	$75.39	$75.40	$75.40
Purchase #2	$184.78	13.636%	$209.9766	$209.98	$210.00	$210.00
Purchase #3	$238.93	6.836%	$255.2633	$255.26	$255.25	$255.30
Purchase #4	$132.66	9.685%	$145.5081	$145.51	$145.50	$145.50
Purchase #5	$59.63	13.369%	$67.6019	$67.60	$67.60	$67.60
Purchase #6	$138.74	9.295%	$151.6359	$151.64	$151.65	$151.60
Purchase #7	$93.34	13.583%	$106.0184	$106.02	$106.00	$106.00
7 purchase totals =	$915.50		$1,011.3919	$1,011.40	$1,011.40	$1,011.40