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	$237.69	4.133%	$247.5137	$247.51	$247.50	$247.50
Purchase #2	$151.61	13.233%	$171.6726	$171.67	$171.65	$171.70
Purchase #3	$218.72	8.712%	$237.7749	$237.77	$237.75	$237.80
Purchase #4	$25.71	12.257%	$28.8613	$28.86	$28.85	$28.90
Purchase #5	$228.25	4.269%	$237.994	$237.99	$238.00	$238.00
Purchase #6	$74.54	5.673%	$78.7687	$78.77	$78.75	$78.80
Purchase #7	$25.60	11.324%	$28.4989	$28.50	$28.50	$28.50
7 purchase totals =	$962.12		$1,031.0841	$1,031.07	$1,031.00	$1,031.20