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	$102.93	13.194%	$116.5106	$116.51	$116.50	$116.50
Purchase #2	$226.94	10.501%	$250.771	$250.77	$250.75	$250.80
Purchase #3	$48.54	4.654%	$50.7991	$50.80	$50.80	$50.80
Purchase #4	$217.32	8.409%	$235.5944	$235.59	$235.60	$235.60
Purchase #5	$64.60	9.208%	$70.5484	$70.55	$70.55	$70.50
Purchase #6	$229.86	6.715%	$245.2951	$245.30	$245.30	$245.30
Purchase #7	$84.60	7.162%	$90.6591	$90.66	$90.65	$90.70
7 purchase totals =	$974.79		$1,060.1777	$1,060.18	$1,060.15	$1,060.20