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	$154.76	11.315%	$172.2711	$172.27	$172.25	$172.30
Purchase #2	$95.81	9.698%	$105.1017	$105.10	$105.10	$105.10
Purchase #3	$141.66	12.228%	$158.9822	$158.98	$159.00	$159.00
Purchase #4	$184.53	7.662%	$198.6687	$198.67	$198.65	$198.70
Purchase #5	$228.47	11.346%	$254.3922	$254.39	$254.40	$254.40
Purchase #6	$149.62	8.863%	$162.8808	$162.88	$162.90	$162.90
Purchase #7	$138.56	10.581%	$153.221	$153.22	$153.20	$153.20
7 purchase totals =	$1,093.41		$1,205.5177	$1,205.51	$1,205.50	$1,205.60