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	$43.72	7.521%	$47.0082	$47.01	$47.00	$47.00
Purchase #2	$73.65	6.204%	$78.2192	$78.22	$78.20	$78.20
Purchase #3	$38.65	5.649%	$40.8333	$40.83	$40.85	$40.80
Purchase #4	$151.42	3.494%	$156.7106	$156.71	$156.70	$156.70
Purchase #5	$167.57	3.402%	$173.2707	$173.27	$173.25	$173.30
Purchase #6	$214.98	6.198%	$228.3045	$228.30	$228.30	$228.30
Purchase #7	$185.80	3.408%	$192.1321	$192.13	$192.15	$192.10
7 purchase totals =	$875.79		$916.4786	$916.47	$916.45	$916.40