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	$92.42	9.748%	$101.4291	$101.43	$101.45	$101.40
Purchase #2	$145.29	4.339%	$151.5941	$151.59	$151.60	$151.60
Purchase #3	$82.86	11.154%	$92.1022	$92.10	$92.10	$92.10
Purchase #4	$68.70	4.394%	$71.7187	$71.72	$71.70	$71.70
Purchase #5	$157.82	3.133%	$162.7645	$162.76	$162.75	$162.80
Purchase #6	$85.80	5.157%	$90.2247	$90.22	$90.20	$90.20
Purchase #7	$57.54	5.255%	$60.5637	$60.56	$60.55	$60.60
7 purchase totals =	$690.43		$730.3970	$730.38	$730.35	$730.40