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	$225.31	10.755%	$249.5421	$249.54	$249.55	$249.50
Purchase #2	$95.72	10.177%	$105.4614	$105.46	$105.45	$105.50
Purchase #3	$216.25	4.267%	$225.4774	$225.48	$225.50	$225.50
Purchase #4	$153.32	3.692%	$158.9806	$158.98	$159.00	$159.00
Purchase #5	$35.75	11.320%	$39.7969	$39.80	$39.80	$39.80
Purchase #6	$127.48	10.242%	$140.5365	$140.54	$140.55	$140.50
Purchase #7	$203.25	10.500%	$224.5913	$224.59	$224.60	$224.60
7 purchase totals =	$1,057.08		$1,144.3862	$1,144.39	$1,144.45	$1,144.40