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	$8.51	3.250%	$8.7866	$8.79	$8.80	$8.80
Purchase #2	$11.45	9.557%	$12.5443	$12.54	$12.55	$12.50
Purchase #3	$53.88	3.674%	$55.8596	$55.86	$55.85	$55.90
Purchase #4	$122.65	4.256%	$127.87	$127.87	$127.85	$127.90
Purchase #5	$71.64	9.119%	$78.1729	$78.17	$78.15	$78.20
Purchase #6	$107.43	4.856%	$112.6468	$112.65	$112.65	$112.60
Purchase #7	$118.89	9.334%	$129.9872	$129.99	$130.00	$130.00
7 purchase totals =	$494.45		$525.8674	$525.87	$525.85	$525.90