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	$157.55	8.353%	$170.7102	$170.71	$170.70	$170.70
Purchase #2	$54.64	8.837%	$59.4685	$59.47	$59.45	$59.50
Purchase #3	$161.47	10.805%	$178.9168	$178.92	$178.90	$178.90
Purchase #4	$109.76	9.236%	$119.8974	$119.90	$119.90	$119.90
Purchase #5	$198.66	9.693%	$217.9161	$217.92	$217.90	$217.90
Purchase #6	$149.60	4.860%	$156.8706	$156.87	$156.85	$156.90
Purchase #7	$51.76	5.515%	$54.6146	$54.61	$54.60	$54.60
7 purchase totals =	$883.44		$958.3942	$958.40	$958.30	$958.40