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	$117.77	13.616%	$133.8056	$133.81	$133.80	$133.80
Purchase #2	$189.31	10.164%	$208.5515	$208.55	$208.55	$208.60
Purchase #3	$208.39	10.763%	$230.819	$230.82	$230.80	$230.80
Purchase #4	$126.39	8.768%	$137.4719	$137.47	$137.45	$137.50
Purchase #5	$215.32	10.758%	$238.4841	$238.48	$238.50	$238.50
Purchase #6	$77.52	6.545%	$82.5937	$82.59	$82.60	$82.60
Purchase #7	$26.75	7.245%	$28.688	$28.69	$28.70	$28.70
7 purchase totals =	$961.45		$1,060.4138	$1,060.41	$1,060.40	$1,060.50