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	$56.40	10.665%	$62.4151	$62.42	$62.40	$62.40
Purchase #2	$193.25	13.731%	$219.7852	$219.79	$219.80	$219.80
Purchase #3	$162.68	13.485%	$184.6174	$184.62	$184.60	$184.60
Purchase #4	$128.42	8.366%	$139.1636	$139.16	$139.15	$139.20
Purchase #5	$18.88	7.277%	$20.2539	$20.25	$20.25	$20.30
Purchase #6	$162.37	3.172%	$167.5204	$167.52	$167.50	$167.50
Purchase #7	$189.38	12.836%	$213.6888	$213.69	$213.70	$213.70
7 purchase totals =	$911.38		$1,007.4444	$1,007.45	$1,007.40	$1,007.50