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	$236.33	4.874%	$247.8487	$247.85	$247.85	$247.80
Purchase #2	$193.88	12.167%	$217.4694	$217.47	$217.45	$217.50
Purchase #3	$17.75	10.438%	$19.6027	$19.60	$19.60	$19.60
Purchase #4	$233.66	3.677%	$242.2517	$242.25	$242.25	$242.30
Purchase #5	$110.89	11.679%	$123.8408	$123.84	$123.85	$123.80
Purchase #6	$243.89	6.440%	$259.5965	$259.60	$259.60	$259.60
Purchase #7	$230.59	10.817%	$255.5329	$255.53	$255.55	$255.50
7 purchase totals =	$1,266.99		$1,366.1427	$1,366.14	$1,366.15	$1,366.10