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	$36.71	3.733%	$38.0804	$38.08	$38.10	$38.10
Purchase #2	$150.25	3.827%	$156.0001	$156.00	$156.00	$156.00
Purchase #3	$78.83	13.302%	$89.316	$89.32	$89.30	$89.30
Purchase #4	$92.80	7.782%	$100.0217	$100.02	$100.00	$100.00
Purchase #5	$165.76	6.510%	$176.551	$176.55	$176.55	$176.60
Purchase #6	$100.74	12.198%	$113.0283	$113.03	$113.05	$113.00
Purchase #7	$108.85	5.326%	$114.6474	$114.65	$114.65	$114.60
7 purchase totals =	$733.94		$787.6449	$787.65	$787.65	$787.60