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	$95.93	10.696%	$106.1907	$106.19	$106.20	$106.20
Purchase #2	$174.93	9.371%	$191.3227	$191.32	$191.30	$191.30
Purchase #3	$54.28	4.519%	$56.7329	$56.73	$56.75	$56.70
Purchase #4	$144.29	12.873%	$162.8645	$162.86	$162.85	$162.90
Purchase #5	$153.64	3.128%	$158.4459	$158.45	$158.45	$158.40
Purchase #6	$40.51	11.844%	$45.308	$45.31	$45.30	$45.30
Purchase #7	$150.42	5.284%	$158.3682	$158.37	$158.35	$158.40
7 purchase totals =	$814.00		$879.2329	$879.23	$879.20	$879.20