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	$149.93	9.283%	$163.848	$163.85	$163.85	$163.80
Purchase #2	$101.59	10.166%	$111.9176	$111.92	$111.90	$111.90
Purchase #3	$217.58	11.222%	$241.9968	$242.00	$242.00	$242.00
Purchase #4	$71.66	13.831%	$81.5713	$81.57	$81.55	$81.60
Purchase #5	$139.70	11.385%	$155.6048	$155.60	$155.60	$155.60
Purchase #6	$57.41	6.868%	$61.3529	$61.35	$61.35	$61.40
Purchase #7	$200.41	13.524%	$227.5134	$227.51	$227.50	$227.50
7 purchase totals =	$938.28		$1,043.8048	$1,043.80	$1,043.75	$1,043.80