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	$35.28	9.239%	$38.5395	$38.54	$38.55	$38.50
Purchase #2	$97.54	3.160%	$100.6223	$100.62	$100.60	$100.60
Purchase #3	$152.46	10.703%	$168.7778	$168.78	$168.80	$168.80
Purchase #4	$197.80	11.343%	$220.2365	$220.24	$220.25	$220.20
Purchase #5	$230.39	8.489%	$249.9478	$249.95	$249.95	$249.90
Purchase #6	$166.29	3.381%	$171.9123	$171.91	$171.90	$171.90
Purchase #7	$107.38	3.738%	$111.3939	$111.39	$111.40	$111.40
7 purchase totals =	$987.14		$1,061.4301	$1,061.43	$1,061.45	$1,061.30