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	$148.95	11.835%	$166.5782	$166.58	$166.60	$166.60
Purchase #2	$233.75	9.721%	$256.4728	$256.47	$256.45	$256.50
Purchase #3	$60.55	9.730%	$66.4415	$66.44	$66.45	$66.40
Purchase #4	$247.79	4.724%	$259.4956	$259.50	$259.50	$259.50
Purchase #5	$18.93	10.734%	$20.9619	$20.96	$20.95	$21.00
Purchase #6	$131.66	11.130%	$146.3138	$146.31	$146.30	$146.30
Purchase #7	$35.94	4.479%	$37.5498	$37.55	$37.55	$37.50
7 purchase totals =	$877.57		$953.8136	$953.81	$953.80	$953.80