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	$119.85	6.393%	$127.512	$127.51	$127.50	$127.50
Purchase #2	$11.30	6.206%	$12.0013	$12.00	$12.00	$12.00
Purchase #3	$161.38	10.847%	$178.8849	$178.88	$178.90	$178.90
Purchase #4	$163.89	13.241%	$185.5907	$185.59	$185.60	$185.60
Purchase #5	$202.39	10.272%	$223.1795	$223.18	$223.20	$223.20
Purchase #6	$225.82	10.110%	$248.6504	$248.65	$248.65	$248.70
Purchase #7	$154.60	8.352%	$167.5122	$167.51	$167.50	$167.50
7 purchase totals =	$1,039.23		$1,143.3310	$1,143.32	$1,143.35	$1,143.40