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	$125.66	11.321%	$139.886	$139.89	$139.90	$139.90
Purchase #2	$43.31	8.400%	$46.948	$46.95	$46.95	$46.90
Purchase #3	$83.45	10.443%	$92.1647	$92.16	$92.15	$92.20
Purchase #4	$48.90	4.716%	$51.2061	$51.21	$51.20	$51.20
Purchase #5	$67.73	7.227%	$72.6248	$72.62	$72.60	$72.60
Purchase #6	$199.73	6.231%	$212.1752	$212.18	$212.20	$212.20
Purchase #7	$140.93	8.466%	$152.8611	$152.86	$152.85	$152.90
7 purchase totals =	$709.71		$767.8659	$767.87	$767.85	$767.90