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	$156.83	12.141%	$175.8707	$175.87	$175.85	$175.90
Purchase #2	$208.28	4.405%	$217.4547	$217.45	$217.45	$217.50
Purchase #3	$18.35	6.289%	$19.504	$19.50	$19.50	$19.50
Purchase #4	$41.35	3.729%	$42.8919	$42.89	$42.90	$42.90
Purchase #5	$132.50	12.221%	$148.6928	$148.69	$148.70	$148.70
Purchase #6	$115.54	8.235%	$125.0547	$125.05	$125.05	$125.10
Purchase #7	$153.50	3.123%	$158.2938	$158.29	$158.30	$158.30
7 purchase totals =	$826.35		$887.7626	$887.74	$887.75	$887.90