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	$235.70	12.735%	$265.7164	$265.72	$265.70	$265.70
Purchase #2	$119.33	3.505%	$123.5125	$123.51	$123.50	$123.50
Purchase #3	$200.27	4.586%	$209.4544	$209.45	$209.45	$209.50
Purchase #4	$112.68	12.836%	$127.1436	$127.14	$127.15	$127.10
Purchase #5	$233.28	12.228%	$261.8055	$261.81	$261.80	$261.80
Purchase #6	$237.97	7.466%	$255.7368	$255.74	$255.75	$255.70
Purchase #7	$76.31	7.265%	$81.8539	$81.85	$81.85	$81.90
7 purchase totals =	$1,215.54		$1,325.2231	$1,325.22	$1,325.20	$1,325.20