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	$102.58	8.822%	$111.6296	$111.63	$111.65	$111.60
Purchase #2	$96.87	12.108%	$108.599	$108.60	$108.60	$108.60
Purchase #3	$93.73	12.506%	$105.4519	$105.45	$105.45	$105.50
Purchase #4	$18.42	4.635%	$19.2738	$19.27	$19.25	$19.30
Purchase #5	$228.61	13.147%	$258.6654	$258.67	$258.65	$258.70
Purchase #6	$58.32	13.576%	$66.2375	$66.24	$66.25	$66.20
Purchase #7	$149.57	7.391%	$160.6247	$160.62	$160.60	$160.60
7 purchase totals =	$748.10		$830.4819	$830.48	$830.45	$830.50