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	$52.29	4.430%	$54.6064	$54.61	$54.60	$54.60
Purchase #2	$29.58	10.397%	$32.6554	$32.66	$32.65	$32.70
Purchase #3	$133.50	7.556%	$143.5873	$143.59	$143.60	$143.60
Purchase #4	$155.88	11.193%	$173.3276	$173.33	$173.35	$173.30
Purchase #5	$247.83	4.356%	$258.6255	$258.63	$258.65	$258.60
Purchase #6	$24.25	6.857%	$25.9128	$25.91	$25.90	$25.90
Purchase #7	$111.52	7.115%	$119.4546	$119.45	$119.45	$119.50
7 purchase totals =	$754.85		$808.1696	$808.18	$808.20	$808.20