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	$45.52	6.564%	$48.5079	$48.51	$48.50	$48.50
Purchase #2	$9.66	4.622%	$10.1065	$10.11	$10.10	$10.10
Purchase #3	$48.46	8.159%	$52.4139	$52.41	$52.40	$52.40
Purchase #4	$83.89	8.414%	$90.9485	$90.95	$90.95	$90.90
Purchase #5	$121.86	7.227%	$130.6668	$130.67	$130.65	$130.70
Purchase #6	$152.61	13.864%	$173.7679	$173.77	$173.75	$173.80
Purchase #7	$245.27	4.672%	$256.729	$256.73	$256.75	$256.70
7 purchase totals =	$707.27		$763.1405	$763.15	$763.10	$763.10