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	$14.68	3.211%	$15.1514	$15.15	$15.15	$15.20
Purchase #2	$37.33	12.499%	$41.9959	$42.00	$42.00	$42.00
Purchase #3	$212.96	11.128%	$236.6582	$236.66	$236.65	$236.70
Purchase #4	$70.87	10.400%	$78.2405	$78.24	$78.25	$78.20
Purchase #5	$168.42	4.485%	$175.9736	$175.97	$175.95	$176.00
Purchase #6	$154.68	11.626%	$172.6631	$172.66	$172.65	$172.70
Purchase #7	$112.97	9.422%	$123.614	$123.61	$123.60	$123.60
7 purchase totals =	$771.91		$844.2967	$844.29	$844.25	$844.40