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	$43.47	5.315%	$45.7804	$45.78	$45.80	$45.80
Purchase #2	$74.72	10.194%	$82.337	$82.34	$82.35	$82.30
Purchase #3	$96.61	3.598%	$100.086	$100.09	$100.10	$100.10
Purchase #4	$83.92	6.798%	$89.6249	$89.62	$89.60	$89.60
Purchase #5	$34.64	12.103%	$38.8325	$38.83	$38.85	$38.80
Purchase #6	$151.42	7.146%	$162.2405	$162.24	$162.25	$162.20
Purchase #7	$152.42	5.873%	$161.3716	$161.37	$161.35	$161.40
7 purchase totals =	$637.20		$680.2729	$680.27	$680.30	$680.20