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	$30.65	8.721%	$33.323	$33.32	$33.30	$33.30
Purchase #2	$89.28	7.447%	$95.9287	$95.93	$95.95	$95.90
Purchase #3	$221.96	5.246%	$233.604	$233.60	$233.60	$233.60
Purchase #4	$74.78	10.426%	$82.5766	$82.58	$82.60	$82.60
Purchase #5	$47.77	12.449%	$53.7169	$53.72	$53.70	$53.70
Purchase #6	$118.62	6.516%	$126.3493	$126.35	$126.35	$126.30
Purchase #7	$109.76	5.706%	$116.0229	$116.02	$116.00	$116.00
7 purchase totals =	$692.82		$741.5214	$741.52	$741.50	$741.40