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	$146.61	13.747%	$166.7645	$166.76	$166.75	$166.80
Purchase #2	$241.71	5.536%	$255.0911	$255.09	$255.10	$255.10
Purchase #3	$214.98	7.690%	$231.512	$231.51	$231.50	$231.50
Purchase #4	$223.73	6.424%	$238.1024	$238.10	$238.10	$238.10
Purchase #5	$29.57	5.409%	$31.1694	$31.17	$31.15	$31.20
Purchase #6	$128.26	8.860%	$139.6238	$139.62	$139.60	$139.60
Purchase #7	$118.26	7.713%	$127.3814	$127.38	$127.40	$127.40
7 purchase totals =	$1,103.12		$1,189.6446	$1,189.63	$1,189.60	$1,189.70