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	$229.43	3.788%	$238.1208	$238.12	$238.10	$238.10
Purchase #2	$126.76	4.692%	$132.7076	$132.71	$132.70	$132.70
Purchase #3	$123.59	12.585%	$139.1438	$139.14	$139.15	$139.10
Purchase #4	$23.44	5.273%	$24.676	$24.68	$24.70	$24.70
Purchase #5	$137.85	4.751%	$144.3993	$144.40	$144.40	$144.40
Purchase #6	$142.48	6.313%	$151.4748	$151.47	$151.45	$151.50
Purchase #7	$231.35	3.292%	$238.966	$238.97	$238.95	$239.00
7 purchase totals =	$1,014.90		$1,069.4883	$1,069.49	$1,069.45	$1,069.50