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	$118.75	12.395%	$133.4691	$133.47	$133.45	$133.50
Purchase #2	$51.98	11.400%	$57.9057	$57.91	$57.90	$57.90
Purchase #3	$119.60	5.387%	$126.0429	$126.04	$126.05	$126.00
Purchase #4	$99.28	13.309%	$112.4932	$112.49	$112.50	$112.50
Purchase #5	$104.58	4.556%	$109.3447	$109.34	$109.35	$109.30
Purchase #6	$56.56	11.102%	$62.8393	$62.84	$62.85	$62.80
Purchase #7	$175.83	13.518%	$199.5987	$199.60	$199.60	$199.60
7 purchase totals =	$726.58		$801.6936	$801.69	$801.70	$801.60