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	$161.50	6.519%	$172.0282	$172.03	$172.05	$172.00
Purchase #2	$152.27	9.103%	$166.1311	$166.13	$166.15	$166.10
Purchase #3	$83.88	9.358%	$91.7295	$91.73	$91.75	$91.70
Purchase #4	$176.72	7.162%	$189.3767	$189.38	$189.40	$189.40
Purchase #5	$26.29	5.654%	$27.7764	$27.78	$27.80	$27.80
Purchase #6	$192.45	9.802%	$211.3139	$211.31	$211.30	$211.30
Purchase #7	$199.37	12.788%	$224.8654	$224.87	$224.85	$224.90
7 purchase totals =	$992.48		$1,083.2212	$1,083.23	$1,083.30	$1,083.20