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	$177.47	8.103%	$191.8504	$191.85	$191.85	$191.90
Purchase #2	$92.75	12.582%	$104.4198	$104.42	$104.40	$104.40
Purchase #3	$20.39	4.195%	$21.2454	$21.25	$21.25	$21.20
Purchase #4	$18.81	10.702%	$20.823	$20.82	$20.80	$20.80
Purchase #5	$166.45	13.201%	$188.4231	$188.42	$188.40	$188.40
Purchase #6	$129.79	7.438%	$139.4438	$139.44	$139.45	$139.40
Purchase #7	$200.41	9.483%	$219.4149	$219.41	$219.40	$219.40
7 purchase totals =	$806.07		$885.6204	$885.61	$885.55	$885.50