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	$164.42	5.436%	$173.3579	$173.36	$173.35	$173.40
Purchase #2	$102.67	8.769%	$111.6731	$111.67	$111.65	$111.70
Purchase #3	$39.63	4.516%	$41.4197	$41.42	$41.40	$41.40
Purchase #4	$45.42	11.635%	$50.7046	$50.70	$50.70	$50.70
Purchase #5	$164.36	9.115%	$179.3414	$179.34	$179.35	$179.30
Purchase #6	$90.81	12.480%	$102.1431	$102.14	$102.15	$102.10
Purchase #7	$153.29	13.418%	$173.8585	$173.86	$173.85	$173.90
7 purchase totals =	$760.60		$832.4983	$832.49	$832.45	$832.50