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	$244.83	8.776%	$266.3163	$266.32	$266.30	$266.30
Purchase #2	$20.67	5.774%	$21.8635	$21.86	$21.85	$21.90
Purchase #3	$72.50	5.643%	$76.5912	$76.59	$76.60	$76.60
Purchase #4	$90.60	4.764%	$94.9162	$94.92	$94.90	$94.90
Purchase #5	$32.85	13.196%	$37.1849	$37.18	$37.20	$37.20
Purchase #6	$205.50	8.263%	$222.4805	$222.48	$222.50	$222.50
Purchase #7	$44.98	3.810%	$46.6937	$46.69	$46.70	$46.70
7 purchase totals =	$711.93		$766.0463	$766.04	$766.05	$766.10