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	$191.86	10.788%	$212.5579	$212.56	$212.55	$212.60
Purchase #2	$130.42	13.349%	$147.8298	$147.83	$147.85	$147.80
Purchase #3	$128.70	10.741%	$142.5237	$142.52	$142.50	$142.50
Purchase #4	$184.66	4.124%	$192.2754	$192.28	$192.30	$192.30
Purchase #5	$105.32	12.719%	$118.7157	$118.72	$118.70	$118.70
Purchase #6	$129.77	6.856%	$138.667	$138.67	$138.65	$138.70
Purchase #7	$132.40	8.648%	$143.85	$143.85	$143.85	$143.90
7 purchase totals =	$1,003.13		$1,096.4195	$1,096.43	$1,096.40	$1,096.50