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	$148.93	8.425%	$161.4774	$161.48	$161.50	$161.50
Purchase #2	$108.80	3.811%	$112.9464	$112.95	$112.95	$112.90
Purchase #3	$117.73	9.503%	$128.9179	$128.92	$128.90	$128.90
Purchase #4	$179.46	10.483%	$198.2728	$198.27	$198.25	$198.30
Purchase #5	$115.60	10.222%	$127.4166	$127.42	$127.40	$127.40
Purchase #6	$222.50	8.694%	$241.8442	$241.84	$241.85	$241.80
Purchase #7	$82.52	9.611%	$90.451	$90.45	$90.45	$90.50
7 purchase totals =	$975.54		$1,061.3263	$1,061.33	$1,061.30	$1,061.30