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	$91.28	8.512%	$99.0498	$99.05	$99.05	$99.00
Purchase #2	$50.27	5.586%	$53.0781	$53.08	$53.10	$53.10
Purchase #3	$85.43	4.491%	$89.2667	$89.27	$89.25	$89.30
Purchase #4	$240.72	9.542%	$263.6895	$263.69	$263.70	$263.70
Purchase #5	$225.52	3.806%	$234.1033	$234.10	$234.10	$234.10
Purchase #6	$215.75	11.641%	$240.8655	$240.87	$240.85	$240.90
Purchase #7	$177.78	10.599%	$196.6229	$196.62	$196.60	$196.60
7 purchase totals =	$1,086.75		$1,176.6758	$1,176.68	$1,176.65	$1,176.70