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	$83.84	13.455%	$95.1207	$95.12	$95.10	$95.10
Purchase #2	$99.47	12.190%	$111.5954	$111.60	$111.60	$111.60
Purchase #3	$116.63	3.156%	$120.3108	$120.31	$120.30	$120.30
Purchase #4	$101.52	4.342%	$105.928	$105.93	$105.95	$105.90
Purchase #5	$234.81	3.220%	$242.3709	$242.37	$242.35	$242.40
Purchase #6	$126.92	4.678%	$132.8573	$132.86	$132.85	$132.90
Purchase #7	$92.77	13.508%	$105.3014	$105.30	$105.30	$105.30
7 purchase totals =	$855.96		$913.4845	$913.49	$913.45	$913.50