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	$192.82	3.417%	$199.4087	$199.41	$199.40	$199.40
Purchase #2	$80.38	7.115%	$86.099	$86.10	$86.10	$86.10
Purchase #3	$138.35	3.360%	$142.9986	$143.00	$143.00	$143.00
Purchase #4	$114.96	10.793%	$127.3676	$127.37	$127.35	$127.40
Purchase #5	$242.31	6.176%	$257.2751	$257.28	$257.30	$257.30
Purchase #6	$33.46	13.320%	$37.9169	$37.92	$37.90	$37.90
Purchase #7	$18.81	13.733%	$21.3932	$21.39	$21.40	$21.40
7 purchase totals =	$821.09		$872.4591	$872.47	$872.45	$872.50