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	$152.55	10.793%	$169.0147	$169.01	$169.00	$169.00
Purchase #2	$34.74	3.132%	$35.8281	$35.83	$35.85	$35.80
Purchase #3	$184.80	3.504%	$191.2754	$191.28	$191.30	$191.30
Purchase #4	$153.27	10.176%	$168.8668	$168.87	$168.85	$168.90
Purchase #5	$97.60	3.149%	$100.6734	$100.67	$100.65	$100.70
Purchase #6	$67.95	3.546%	$70.3595	$70.36	$70.35	$70.40
Purchase #7	$217.83	7.128%	$233.3569	$233.36	$233.35	$233.40
7 purchase totals =	$908.74		$969.3748	$969.38	$969.35	$969.50