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	$70.72	9.436%	$77.3931	$77.39	$77.40	$77.40
Purchase #2	$131.70	9.200%	$143.8164	$143.82	$143.80	$143.80
Purchase #3	$246.65	6.572%	$262.8598	$262.86	$262.85	$262.90
Purchase #4	$138.64	9.722%	$152.1186	$152.12	$152.10	$152.10
Purchase #5	$61.35	4.640%	$64.1966	$64.20	$64.20	$64.20
Purchase #6	$217.45	9.533%	$238.1795	$238.18	$238.20	$238.20
Purchase #7	$237.60	10.205%	$261.8471	$261.85	$261.85	$261.80
7 purchase totals =	$1,104.11		$1,200.4111	$1,200.42	$1,200.40	$1,200.40