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	$30.99	3.866%	$32.1881	$32.19	$32.20	$32.20
Purchase #2	$26.79	10.272%	$29.5419	$29.54	$29.55	$29.50
Purchase #3	$151.91	13.612%	$172.588	$172.59	$172.60	$172.60
Purchase #4	$166.44	11.846%	$186.1565	$186.16	$186.15	$186.20
Purchase #5	$220.37	7.491%	$236.8779	$236.88	$236.90	$236.90
Purchase #6	$132.27	10.665%	$146.3766	$146.38	$146.40	$146.40
Purchase #7	$207.56	6.729%	$221.5267	$221.53	$221.55	$221.50
7 purchase totals =	$936.33		$1,025.2557	$1,025.27	$1,025.35	$1,025.30