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	$170.75	4.273%	$178.0461	$178.05	$178.05	$178.00
Purchase #2	$176.30	4.720%	$184.6214	$184.62	$184.60	$184.60
Purchase #3	$226.95	4.603%	$237.3965	$237.40	$237.40	$237.40
Purchase #4	$89.68	10.268%	$98.8883	$98.89	$98.90	$98.90
Purchase #5	$51.67	10.164%	$56.9217	$56.92	$56.90	$56.90
Purchase #6	$79.53	12.632%	$89.5762	$89.58	$89.60	$89.60
Purchase #7	$189.72	8.235%	$205.3434	$205.34	$205.35	$205.30
7 purchase totals =	$984.60		$1,050.7936	$1,050.80	$1,050.80	$1,050.70