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	$178.93	10.439%	$197.6085	$197.61	$197.60	$197.60
Purchase #2	$143.43	5.180%	$150.8597	$150.86	$150.85	$150.90
Purchase #3	$226.56	5.465%	$238.9415	$238.94	$238.95	$238.90
Purchase #4	$243.44	13.175%	$275.5132	$275.51	$275.50	$275.50
Purchase #5	$107.61	10.150%	$118.5324	$118.53	$118.55	$118.50
Purchase #6	$118.31	10.316%	$130.5149	$130.51	$130.50	$130.50
Purchase #7	$135.40	5.242%	$142.4977	$142.50	$142.50	$142.50
7 purchase totals =	$1,153.68		$1,254.4679	$1,254.46	$1,254.45	$1,254.40