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	$102.54	8.705%	$111.4661	$111.47	$111.45	$111.50
Purchase #2	$236.71	8.429%	$256.6623	$256.66	$256.65	$256.70
Purchase #3	$121.93	4.585%	$127.5205	$127.52	$127.50	$127.50
Purchase #4	$203.35	12.200%	$228.1587	$228.16	$228.15	$228.20
Purchase #5	$189.58	7.149%	$203.1331	$203.13	$203.15	$203.10
Purchase #6	$244.32	12.799%	$275.5905	$275.59	$275.60	$275.60
Purchase #7	$159.97	9.135%	$174.5833	$174.58	$174.60	$174.60
7 purchase totals =	$1,258.40		$1,377.1145	$1,377.11	$1,377.10	$1,377.20