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	$67.94	4.731%	$71.1542	$71.15	$71.15	$71.20
Purchase #2	$188.56	12.823%	$212.739	$212.74	$212.75	$212.70
Purchase #3	$227.53	4.723%	$238.2762	$238.28	$238.30	$238.30
Purchase #4	$105.34	12.130%	$118.1177	$118.12	$118.10	$118.10
Purchase #5	$35.40	9.643%	$38.8136	$38.81	$38.80	$38.80
Purchase #6	$154.88	10.798%	$171.6039	$171.60	$171.60	$171.60
Purchase #7	$171.58	8.153%	$185.5689	$185.57	$185.55	$185.60
7 purchase totals =	$951.23		$1,036.2735	$1,036.27	$1,036.25	$1,036.30