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	$159.86	11.292%	$177.9114	$177.91	$177.90	$177.90
Purchase #2	$10.50	13.642%	$11.9324	$11.93	$11.95	$11.90
Purchase #3	$38.76	9.119%	$42.2945	$42.29	$42.30	$42.30
Purchase #4	$155.39	5.845%	$164.4725	$164.47	$164.45	$164.50
Purchase #5	$114.84	3.559%	$118.9272	$118.93	$118.95	$118.90
Purchase #6	$235.34	11.791%	$263.0889	$263.09	$263.10	$263.10
Purchase #7	$181.78	9.712%	$199.4345	$199.43	$199.45	$199.40
7 purchase totals =	$896.47		$978.0614	$978.05	$978.10	$978.00