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	$200.90	8.320%	$217.6149	$217.61	$217.60	$217.60
Purchase #2	$225.86	7.234%	$242.1987	$242.20	$242.20	$242.20
Purchase #3	$10.90	9.370%	$11.9213	$11.92	$11.90	$11.90
Purchase #4	$80.53	10.785%	$89.2152	$89.22	$89.20	$89.20
Purchase #5	$172.47	13.154%	$195.1567	$195.16	$195.15	$195.20
Purchase #6	$231.26	10.446%	$255.4174	$255.42	$255.40	$255.40
Purchase #7	$118.47	9.222%	$129.3953	$129.40	$129.40	$129.40
7 purchase totals =	$1,040.39		$1,140.9195	$1,140.93	$1,140.85	$1,140.90