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	$125.76	3.565%	$130.2433	$130.24	$130.25	$130.20
Purchase #2	$152.50	3.771%	$158.2508	$158.25	$158.25	$158.30
Purchase #3	$228.90	12.303%	$257.0616	$257.06	$257.05	$257.10
Purchase #4	$245.32	11.247%	$272.9111	$272.91	$272.90	$272.90
Purchase #5	$45.66	6.665%	$48.7032	$48.70	$48.70	$48.70
Purchase #6	$158.31	8.212%	$171.3104	$171.31	$171.30	$171.30
Purchase #7	$92.37	13.714%	$105.0376	$105.04	$105.05	$105.00
7 purchase totals =	$1,048.82		$1,143.5180	$1,143.51	$1,143.50	$1,143.50