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	$242.68	8.209%	$262.6016	$262.60	$262.60	$262.60
Purchase #2	$172.64	13.852%	$196.5541	$196.55	$196.55	$196.60
Purchase #3	$113.62	9.647%	$124.5809	$124.58	$124.60	$124.60
Purchase #4	$102.83	6.714%	$109.734	$109.73	$109.75	$109.70
Purchase #5	$101.91	7.390%	$109.4411	$109.44	$109.45	$109.40
Purchase #6	$113.86	8.253%	$123.2569	$123.26	$123.25	$123.30
Purchase #7	$222.88	9.228%	$243.4474	$243.45	$243.45	$243.40
7 purchase totals =	$1,070.42		$1,169.6160	$1,169.61	$1,169.65	$1,169.60