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	$153.37	4.700%	$160.5784	$160.58	$160.60	$160.60
Purchase #2	$94.59	13.254%	$107.127	$107.13	$107.15	$107.10
Purchase #3	$240.80	10.163%	$265.2725	$265.27	$265.25	$265.30
Purchase #4	$44.54	12.152%	$49.9525	$49.95	$49.95	$50.00
Purchase #5	$104.56	6.603%	$111.4641	$111.46	$111.45	$111.50
Purchase #6	$172.49	4.722%	$180.635	$180.64	$180.65	$180.60
Purchase #7	$236.44	3.559%	$244.8549	$244.85	$244.85	$244.90
7 purchase totals =	$1,046.79		$1,119.8844	$1,119.88	$1,119.90	$1,120.00