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	$213.96	13.346%	$242.5151	$242.52	$242.50	$242.50
Purchase #2	$77.94	5.532%	$82.2516	$82.25	$82.25	$82.30
Purchase #3	$59.89	10.440%	$66.1425	$66.14	$66.15	$66.10
Purchase #4	$217.67	7.752%	$234.5438	$234.54	$234.55	$234.50
Purchase #5	$164.64	9.110%	$179.6387	$179.64	$179.65	$179.60
Purchase #6	$112.68	10.693%	$124.7289	$124.73	$124.75	$124.70
Purchase #7	$11.44	9.348%	$12.5094	$12.51	$12.50	$12.50
7 purchase totals =	$858.22		$942.3300	$942.33	$942.35	$942.20