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	$123.57	7.680%	$133.0602	$133.06	$133.05	$133.10
Purchase #2	$173.60	11.293%	$193.2046	$193.20	$193.20	$193.20
Purchase #3	$104.90	4.383%	$109.4978	$109.50	$109.50	$109.50
Purchase #4	$36.84	11.207%	$40.9687	$40.97	$40.95	$41.00
Purchase #5	$100.58	9.151%	$109.7841	$109.78	$109.80	$109.80
Purchase #6	$106.87	4.125%	$111.2784	$111.28	$111.30	$111.30
Purchase #7	$59.77	10.466%	$66.0255	$66.03	$66.05	$66.00
7 purchase totals =	$706.13		$763.8193	$763.82	$763.85	$763.90