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	$12.85	12.532%	$14.4604	$14.46	$14.45	$14.50
Purchase #2	$166.52	12.242%	$186.9054	$186.91	$186.90	$186.90
Purchase #3	$121.38	5.341%	$127.8629	$127.86	$127.85	$127.90
Purchase #4	$222.58	6.824%	$237.7689	$237.77	$237.75	$237.80
Purchase #5	$27.25	9.768%	$29.9118	$29.91	$29.90	$29.90
Purchase #6	$157.91	10.454%	$174.4179	$174.42	$174.40	$174.40
Purchase #7	$216.65	6.631%	$231.0161	$231.02	$231.00	$231.00
7 purchase totals =	$925.14		$1,002.3434	$1,002.35	$1,002.25	$1,002.40