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	$120.75	11.121%	$134.1786	$134.18	$134.20	$134.20
Purchase #2	$59.93	6.723%	$63.9591	$63.96	$63.95	$64.00
Purchase #3	$157.89	5.317%	$166.285	$166.29	$166.30	$166.30
Purchase #4	$96.65	4.361%	$100.8649	$100.86	$100.85	$100.90
Purchase #5	$243.85	4.767%	$255.4743	$255.47	$255.45	$255.50
Purchase #6	$107.84	9.768%	$118.3738	$118.37	$118.35	$118.40
Purchase #7	$180.37	7.787%	$194.4154	$194.42	$194.40	$194.40
7 purchase totals =	$967.28		$1,033.5511	$1,033.55	$1,033.50	$1,033.70