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	$172.59	11.750%	$192.8693	$192.87	$192.85	$192.90
Purchase #2	$131.71	9.330%	$143.9985	$144.00	$144.00	$144.00
Purchase #3	$47.35	12.251%	$53.1508	$53.15	$53.15	$53.20
Purchase #4	$207.32	9.298%	$226.5966	$226.60	$226.60	$226.60
Purchase #5	$130.38	11.105%	$144.8587	$144.86	$144.85	$144.90
Purchase #6	$161.30	10.559%	$178.3317	$178.33	$178.35	$178.30
Purchase #7	$196.65	13.706%	$223.6028	$223.60	$223.60	$223.60
7 purchase totals =	$1,047.30		$1,163.4084	$1,163.41	$1,163.40	$1,163.50