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	$29.51	9.536%	$32.3241	$32.32	$32.30	$32.30
Purchase #2	$244.44	6.544%	$260.4362	$260.44	$260.45	$260.40
Purchase #3	$180.95	4.421%	$188.9498	$188.95	$188.95	$188.90
Purchase #4	$205.56	3.509%	$212.7731	$212.77	$212.75	$212.80
Purchase #5	$112.74	3.706%	$116.9181	$116.92	$116.90	$116.90
Purchase #6	$213.28	8.681%	$231.7948	$231.79	$231.80	$231.80
Purchase #7	$17.41	5.695%	$18.4015	$18.40	$18.40	$18.40
7 purchase totals =	$1,003.89		$1,061.5976	$1,061.59	$1,061.55	$1,061.50