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	$190.98	11.845%	$213.6016	$213.60	$213.60	$213.60
Purchase #2	$99.85	11.397%	$111.2299	$111.23	$111.25	$111.20
Purchase #3	$131.49	8.424%	$142.5667	$142.57	$142.55	$142.60
Purchase #4	$66.52	3.423%	$68.797	$68.80	$68.80	$68.80
Purchase #5	$25.59	5.536%	$27.0067	$27.01	$27.00	$27.00
Purchase #6	$202.95	12.397%	$228.1097	$228.11	$228.10	$228.10
Purchase #7	$97.68	11.835%	$109.2404	$109.24	$109.25	$109.20
7 purchase totals =	$815.06		$900.5520	$900.56	$900.55	$900.50