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	$40.82	7.444%	$43.8586	$43.86	$43.85	$43.90
Purchase #2	$19.68	10.344%	$21.7157	$21.72	$21.70	$21.70
Purchase #3	$150.99	9.124%	$164.7663	$164.77	$164.75	$164.80
Purchase #4	$145.75	5.213%	$153.3479	$153.35	$153.35	$153.30
Purchase #5	$46.35	10.296%	$51.1222	$51.12	$51.10	$51.10
Purchase #6	$22.54	10.528%	$24.913	$24.91	$24.90	$24.90
Purchase #7	$57.31	9.820%	$62.9378	$62.94	$62.95	$62.90
7 purchase totals =	$483.44		$522.6615	$522.67	$522.60	$522.60