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	$130.60	12.517%	$146.9472	$146.95	$146.95	$146.90
Purchase #2	$224.73	8.645%	$244.1579	$244.16	$244.15	$244.20
Purchase #3	$70.43	11.730%	$78.6914	$78.69	$78.70	$78.70
Purchase #4	$111.98	9.845%	$123.0044	$123.00	$123.00	$123.00
Purchase #5	$175.58	11.813%	$196.3213	$196.32	$196.30	$196.30
Purchase #6	$24.32	7.512%	$26.1469	$26.15	$26.15	$26.10
Purchase #7	$12.91	6.323%	$13.7263	$13.73	$13.75	$13.70
7 purchase totals =	$750.55		$828.9954	$829.00	$829.00	$828.90