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	$144.77	11.421%	$161.3042	$161.30	$161.30	$161.30
Purchase #2	$212.92	10.116%	$234.459	$234.46	$234.45	$234.50
Purchase #3	$207.40	7.322%	$222.5858	$222.59	$222.60	$222.60
Purchase #4	$66.90	4.842%	$70.1393	$70.14	$70.15	$70.10
Purchase #5	$158.67	4.851%	$166.3671	$166.37	$166.35	$166.40
Purchase #6	$156.52	5.624%	$165.3227	$165.32	$165.30	$165.30
Purchase #7	$37.38	11.447%	$41.6589	$41.66	$41.65	$41.70
7 purchase totals =	$984.56		$1,061.8370	$1,061.84	$1,061.80	$1,061.90