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	$54.81	7.539%	$58.9421	$58.94	$58.95	$58.90
Purchase #2	$156.39	10.356%	$172.5857	$172.59	$172.60	$172.60
Purchase #3	$69.66	6.388%	$74.1099	$74.11	$74.10	$74.10
Purchase #4	$120.47	13.483%	$136.713	$136.71	$136.70	$136.70
Purchase #5	$28.72	13.346%	$32.553	$32.55	$32.55	$32.60
Purchase #6	$95.57	5.205%	$100.5444	$100.54	$100.55	$100.50
Purchase #7	$71.91	10.246%	$79.2779	$79.28	$79.30	$79.30
7 purchase totals =	$597.53		$654.7260	$654.72	$654.75	$654.70