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	$41.31	12.416%	$46.439	$46.44	$46.45	$46.40
Purchase #2	$37.64	11.392%	$41.9279	$41.93	$41.95	$41.90
Purchase #3	$164.79	5.533%	$173.9078	$173.91	$173.90	$173.90
Purchase #4	$51.25	6.488%	$54.5751	$54.58	$54.60	$54.60
Purchase #5	$49.62	3.610%	$51.4113	$51.41	$51.40	$51.40
Purchase #6	$228.81	4.188%	$238.3926	$238.39	$238.40	$238.40
Purchase #7	$101.76	7.164%	$109.0501	$109.05	$109.05	$109.10
7 purchase totals =	$675.18		$715.7038	$715.71	$715.75	$715.70