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	$86.75	10.393%	$95.7659	$95.77	$95.75	$95.80
Purchase #2	$99.34	4.230%	$103.5421	$103.54	$103.55	$103.50
Purchase #3	$124.39	7.723%	$133.9966	$134.00	$134.00	$134.00
Purchase #4	$101.35	7.169%	$108.6158	$108.62	$108.60	$108.60
Purchase #5	$132.93	10.190%	$146.4756	$146.48	$146.50	$146.50
Purchase #6	$183.33	7.185%	$196.5023	$196.50	$196.50	$196.50
Purchase #7	$55.42	4.417%	$57.8679	$57.87	$57.85	$57.90
7 purchase totals =	$783.51		$842.7662	$842.78	$842.75	$842.80