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	$211.50	4.339%	$220.677	$220.68	$220.70	$220.70
Purchase #2	$160.86	5.863%	$170.2912	$170.29	$170.30	$170.30
Purchase #3	$57.58	13.569%	$65.393	$65.39	$65.40	$65.40
Purchase #4	$118.96	3.839%	$123.5269	$123.53	$123.55	$123.50
Purchase #5	$232.99	10.288%	$256.96	$256.96	$256.95	$257.00
Purchase #6	$160.76	7.847%	$173.3748	$173.37	$173.35	$173.40
Purchase #7	$61.51	9.466%	$67.3325	$67.33	$67.35	$67.30
7 purchase totals =	$1,004.16		$1,077.5554	$1,077.55	$1,077.60	$1,077.60