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	$218.66	5.532%	$230.7563	$230.76	$230.75	$230.80
Purchase #2	$50.58	8.528%	$54.8935	$54.89	$54.90	$54.90
Purchase #3	$114.83	3.587%	$118.949	$118.95	$118.95	$118.90
Purchase #4	$76.30	3.316%	$78.8301	$78.83	$78.85	$78.80
Purchase #5	$90.90	13.489%	$103.1615	$103.16	$103.15	$103.20
Purchase #6	$33.41	6.582%	$35.609	$35.61	$35.60	$35.60
Purchase #7	$51.77	11.630%	$57.7909	$57.79	$57.80	$57.80
7 purchase totals =	$636.45		$679.9903	$679.99	$680.00	$680.00