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	$132.78	13.659%	$150.9164	$150.92	$150.90	$150.90
Purchase #2	$126.69	12.603%	$142.6567	$142.66	$142.65	$142.70
Purchase #3	$7.54	12.435%	$8.4776	$8.48	$8.50	$8.50
Purchase #4	$8.69	13.723%	$9.8825	$9.88	$9.90	$9.90
Purchase #5	$77.72	10.712%	$86.0454	$86.05	$86.05	$86.00
Purchase #6	$39.62	6.268%	$42.1034	$42.10	$42.10	$42.10
Purchase #7	$148.52	6.826%	$158.658	$158.66	$158.65	$158.70
7 purchase totals =	$541.56		$598.7400	$598.75	$598.75	$598.80