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	$237.57	6.873%	$253.8982	$253.90	$253.90	$253.90
Purchase #2	$186.62	7.252%	$200.1537	$200.15	$200.15	$200.20
Purchase #3	$189.97	13.842%	$216.2656	$216.27	$216.25	$216.30
Purchase #4	$53.98	7.453%	$58.0031	$58.00	$58.00	$58.00
Purchase #5	$105.52	5.657%	$111.4893	$111.49	$111.50	$111.50
Purchase #6	$179.28	6.204%	$190.4025	$190.40	$190.40	$190.40
Purchase #7	$19.32	11.777%	$21.5953	$21.60	$21.60	$21.60
7 purchase totals =	$972.26		$1,051.8077	$1,051.81	$1,051.80	$1,051.90