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	$87.87	8.510%	$95.3477	$95.35	$95.35	$95.30
Purchase #2	$148.57	13.391%	$168.465	$168.47	$168.45	$168.50
Purchase #3	$27.33	13.785%	$31.0974	$31.10	$31.10	$31.10
Purchase #4	$100.55	11.563%	$112.1766	$112.18	$112.20	$112.20
Purchase #5	$6.57	5.118%	$6.9063	$6.91	$6.90	$6.90
Purchase #6	$9.65	11.678%	$10.7769	$10.78	$10.80	$10.80
Purchase #7	$118.36	4.146%	$123.2672	$123.27	$123.25	$123.30
7 purchase totals =	$498.90		$548.0371	$548.06	$548.05	$548.10