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	$235.94	6.124%	$250.389	$250.39	$250.40	$250.40
Purchase #2	$153.40	7.300%	$164.5982	$164.60	$164.60	$164.60
Purchase #3	$161.50	7.706%	$173.9452	$173.95	$173.95	$173.90
Purchase #4	$233.41	12.469%	$262.5139	$262.51	$262.50	$262.50
Purchase #5	$67.43	10.220%	$74.3213	$74.32	$74.30	$74.30
Purchase #6	$98.58	6.655%	$105.1405	$105.14	$105.15	$105.10
Purchase #7	$122.90	13.291%	$139.2346	$139.23	$139.25	$139.20
7 purchase totals =	$1,073.16		$1,170.1427	$1,170.14	$1,170.15	$1,170.00