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	$165.95	5.718%	$175.439	$175.44	$175.45	$175.40
Purchase #2	$107.90	3.590%	$111.7736	$111.77	$111.75	$111.80
Purchase #3	$148.67	11.273%	$165.4296	$165.43	$165.45	$165.40
Purchase #4	$40.27	5.275%	$42.3942	$42.39	$42.40	$42.40
Purchase #5	$226.81	12.448%	$255.0433	$255.04	$255.05	$255.00
Purchase #6	$40.46	12.674%	$45.5879	$45.59	$45.60	$45.60
Purchase #7	$155.67	5.440%	$164.1384	$164.14	$164.15	$164.10
7 purchase totals =	$885.73		$959.8060	$959.80	$959.85	$959.70