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	$183.60	8.871%	$199.8872	$199.89	$199.90	$199.90
Purchase #2	$53.57	6.698%	$57.1581	$57.16	$57.15	$57.20
Purchase #3	$143.42	9.145%	$156.5358	$156.54	$156.55	$156.50
Purchase #4	$212.29	13.866%	$241.7261	$241.73	$241.75	$241.70
Purchase #5	$128.92	11.126%	$143.2636	$143.26	$143.25	$143.30
Purchase #6	$99.81	4.535%	$104.3364	$104.34	$104.35	$104.30
Purchase #7	$48.31	8.410%	$52.3729	$52.37	$52.35	$52.40
7 purchase totals =	$869.92		$955.2801	$955.29	$955.30	$955.30