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	$148.93	11.187%	$165.5908	$165.59	$165.60	$165.60
Purchase #2	$244.37	13.764%	$278.0051	$278.01	$278.00	$278.00
Purchase #3	$134.74	5.787%	$142.5374	$142.54	$142.55	$142.50
Purchase #4	$207.58	7.144%	$222.4095	$222.41	$222.40	$222.40
Purchase #5	$189.52	13.169%	$214.4779	$214.48	$214.50	$214.50
Purchase #6	$54.43	4.146%	$56.6867	$56.69	$56.70	$56.70
Purchase #7	$244.29	11.611%	$272.6545	$272.65	$272.65	$272.70
7 purchase totals =	$1,223.86		$1,352.3619	$1,352.37	$1,352.40	$1,352.40