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	$102.77	8.337%	$111.3379	$111.34	$111.35	$111.30
Purchase #2	$113.59	3.164%	$117.184	$117.18	$117.20	$117.20
Purchase #3	$6.91	5.468%	$7.2878	$7.29	$7.30	$7.30
Purchase #4	$80.60	10.517%	$89.0767	$89.08	$89.10	$89.10
Purchase #5	$127.87	3.403%	$132.2214	$132.22	$132.20	$132.20
Purchase #6	$46.51	12.529%	$52.3372	$52.34	$52.35	$52.30
Purchase #7	$199.62	5.112%	$209.8246	$209.82	$209.80	$209.80
7 purchase totals =	$677.87		$719.2696	$719.27	$719.30	$719.20