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	$164.37	12.366%	$184.696	$184.70	$184.70	$184.70
Purchase #2	$85.96	6.702%	$91.721	$91.72	$91.70	$91.70
Purchase #3	$205.88	6.697%	$219.6678	$219.67	$219.65	$219.70
Purchase #4	$61.53	6.631%	$65.6101	$65.61	$65.60	$65.60
Purchase #5	$226.77	8.839%	$246.8142	$246.81	$246.80	$246.80
Purchase #6	$116.86	5.383%	$123.1506	$123.15	$123.15	$123.20
Purchase #7	$192.85	8.862%	$209.9404	$209.94	$209.95	$209.90
7 purchase totals =	$1,054.22		$1,141.6001	$1,141.60	$1,141.55	$1,141.60