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	$97.47	4.306%	$101.6671	$101.67	$101.65	$101.70
Purchase #2	$74.27	10.382%	$81.9807	$81.98	$82.00	$82.00
Purchase #3	$38.75	13.476%	$43.972	$43.97	$43.95	$44.00
Purchase #4	$80.68	10.623%	$89.2506	$89.25	$89.25	$89.30
Purchase #5	$154.54	6.164%	$164.0658	$164.07	$164.05	$164.10
Purchase #6	$58.80	12.269%	$66.0142	$66.01	$66.00	$66.00
Purchase #7	$145.74	5.400%	$153.61	$153.61	$153.60	$153.60
7 purchase totals =	$650.25		$700.5604	$700.56	$700.50	$700.70