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	$143.68	11.559%	$160.288	$160.29	$160.30	$160.30
Purchase #2	$178.43	7.582%	$191.9586	$191.96	$191.95	$192.00
Purchase #3	$127.58	7.225%	$136.7977	$136.80	$136.80	$136.80
Purchase #4	$133.28	9.166%	$145.4964	$145.50	$145.50	$145.50
Purchase #5	$81.30	11.418%	$90.5828	$90.58	$90.60	$90.60
Purchase #6	$114.46	3.342%	$118.2853	$118.29	$118.30	$118.30
Purchase #7	$173.74	11.146%	$193.1051	$193.11	$193.10	$193.10
7 purchase totals =	$952.47		$1,036.5139	$1,036.53	$1,036.55	$1,036.60