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	$234.46	9.103%	$255.8029	$255.80	$255.80	$255.80
Purchase #2	$82.54	5.187%	$86.8213	$86.82	$86.80	$86.80
Purchase #3	$14.92	6.570%	$15.9002	$15.90	$15.90	$15.90
Purchase #4	$228.95	8.288%	$247.9254	$247.93	$247.95	$247.90
Purchase #5	$39.81	9.580%	$43.6238	$43.62	$43.60	$43.60
Purchase #6	$227.30	3.143%	$234.444	$234.44	$234.45	$234.40
Purchase #7	$223.56	4.291%	$233.153	$233.15	$233.15	$233.20
7 purchase totals =	$1,051.54		$1,117.6706	$1,117.66	$1,117.65	$1,117.60