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	$204.25	7.409%	$219.3829	$219.38	$219.40	$219.40
Purchase #2	$230.34	3.603%	$238.6392	$238.64	$238.65	$238.60
Purchase #3	$36.57	12.419%	$41.1116	$41.11	$41.10	$41.10
Purchase #4	$66.81	6.275%	$71.0023	$71.00	$71.00	$71.00
Purchase #5	$38.33	11.103%	$42.5858	$42.59	$42.60	$42.60
Purchase #6	$123.96	10.844%	$137.4022	$137.40	$137.40	$137.40
Purchase #7	$149.93	13.173%	$169.6803	$169.68	$169.70	$169.70
7 purchase totals =	$850.19		$919.8043	$919.80	$919.85	$919.80