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	$62.72	11.349%	$69.8381	$69.84	$69.85	$69.80
Purchase #2	$199.60	13.390%	$226.3264	$226.33	$226.35	$226.30
Purchase #3	$73.80	12.249%	$82.8398	$82.84	$82.85	$82.80
Purchase #4	$18.78	12.667%	$21.1589	$21.16	$21.15	$21.20
Purchase #5	$122.93	6.697%	$131.1626	$131.16	$131.15	$131.20
Purchase #6	$75.54	7.726%	$81.3762	$81.38	$81.40	$81.40
Purchase #7	$117.88	11.495%	$131.4303	$131.43	$131.45	$131.40
7 purchase totals =	$671.25		$744.1323	$744.14	$744.20	$744.10