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	$151.28	7.828%	$163.1222	$163.12	$163.10	$163.10
Purchase #2	$113.68	12.267%	$127.6251	$127.63	$127.65	$127.60
Purchase #3	$128.47	11.256%	$142.9306	$142.93	$142.95	$142.90
Purchase #4	$140.94	10.339%	$155.5118	$155.51	$155.50	$155.50
Purchase #5	$224.67	13.258%	$254.4567	$254.46	$254.45	$254.50
Purchase #6	$129.83	5.357%	$136.785	$136.79	$136.80	$136.80
Purchase #7	$62.57	12.123%	$70.1554	$70.16	$70.15	$70.20
7 purchase totals =	$951.44		$1,050.5868	$1,050.60	$1,050.60	$1,050.60