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	$95.69	9.332%	$104.6198	$104.62	$104.60	$104.60
Purchase #2	$58.61	10.433%	$64.7248	$64.72	$64.70	$64.70
Purchase #3	$132.50	12.365%	$148.8836	$148.88	$148.90	$148.90
Purchase #4	$206.46	6.818%	$220.5364	$220.54	$220.55	$220.50
Purchase #5	$115.98	6.569%	$123.5987	$123.60	$123.60	$123.60
Purchase #6	$52.77	4.502%	$55.1457	$55.15	$55.15	$55.10
Purchase #7	$17.51	5.433%	$18.4613	$18.46	$18.45	$18.50
7 purchase totals =	$679.52		$735.9703	$735.97	$735.95	$735.90