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	$173.87	6.785%	$185.6671	$185.67	$185.65	$185.70
Purchase #2	$197.84	3.863%	$205.4826	$205.48	$205.50	$205.50
Purchase #3	$30.52	6.733%	$32.5749	$32.57	$32.55	$32.60
Purchase #4	$123.39	13.409%	$139.9354	$139.94	$139.95	$139.90
Purchase #5	$147.47	7.321%	$158.2663	$158.27	$158.25	$158.30
Purchase #6	$187.70	4.841%	$196.7866	$196.79	$196.80	$196.80
Purchase #7	$201.32	8.409%	$218.249	$218.25	$218.25	$218.20
7 purchase totals =	$1,062.11		$1,136.9619	$1,136.97	$1,136.95	$1,137.00