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	$44.42	3.112%	$45.8024	$45.80	$45.80	$45.80
Purchase #2	$193.60	5.520%	$204.2867	$204.29	$204.30	$204.30
Purchase #3	$211.83	10.181%	$233.3964	$233.40	$233.40	$233.40
Purchase #4	$166.41	4.372%	$173.6854	$173.69	$173.70	$173.70
Purchase #5	$55.88	4.336%	$58.303	$58.30	$58.30	$58.30
Purchase #6	$29.26	11.828%	$32.7209	$32.72	$32.70	$32.70
Purchase #7	$65.57	10.102%	$72.1939	$72.19	$72.20	$72.20
7 purchase totals =	$766.97		$820.3887	$820.39	$820.40	$820.40