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	$185.67	11.302%	$206.6544	$206.65	$206.65	$206.70
Purchase #2	$106.94	4.239%	$111.4732	$111.47	$111.45	$111.50
Purchase #3	$29.83	11.598%	$33.2897	$33.29	$33.30	$33.30
Purchase #4	$138.32	6.195%	$146.8889	$146.89	$146.90	$146.90
Purchase #5	$82.27	5.291%	$86.6229	$86.62	$86.60	$86.60
Purchase #6	$190.74	9.832%	$209.4936	$209.49	$209.50	$209.50
Purchase #7	$184.75	13.119%	$208.9874	$208.99	$209.00	$209.00
7 purchase totals =	$918.52		$1,003.4101	$1,003.40	$1,003.40	$1,003.50