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	$95.72	10.115%	$105.4021	$105.40	$105.40	$105.40
Purchase #2	$41.95	12.464%	$47.1786	$47.18	$47.20	$47.20
Purchase #3	$78.39	4.833%	$82.1786	$82.18	$82.20	$82.20
Purchase #4	$52.39	12.283%	$58.8251	$58.83	$58.85	$58.80
Purchase #5	$92.56	9.208%	$101.0829	$101.08	$101.10	$101.10
Purchase #6	$97.76	13.841%	$111.291	$111.29	$111.30	$111.30
Purchase #7	$40.57	4.125%	$42.2435	$42.24	$42.25	$42.20
7 purchase totals =	$499.34		$548.2018	$548.20	$548.30	$548.20