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	$222.41	3.318%	$229.7896	$229.79	$229.80	$229.80
Purchase #2	$114.62	7.443%	$123.1512	$123.15	$123.15	$123.20
Purchase #3	$109.39	7.362%	$117.4433	$117.44	$117.45	$117.40
Purchase #4	$122.38	4.286%	$127.6252	$127.63	$127.65	$127.60
Purchase #5	$234.57	8.765%	$255.1301	$255.13	$255.15	$255.10
Purchase #6	$185.69	11.501%	$207.0462	$207.05	$207.05	$207.00
Purchase #7	$98.94	9.567%	$108.4056	$108.41	$108.40	$108.40
7 purchase totals =	$1,088.00		$1,168.5912	$1,168.60	$1,168.65	$1,168.50