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	$242.86	13.683%	$276.0905	$276.09	$276.10	$276.10
Purchase #2	$215.37	12.127%	$241.4879	$241.49	$241.50	$241.50
Purchase #3	$152.38	10.163%	$167.8664	$167.87	$167.85	$167.90
Purchase #4	$150.57	10.223%	$165.9628	$165.96	$165.95	$166.00
Purchase #5	$101.90	5.613%	$107.6196	$107.62	$107.60	$107.60
Purchase #6	$65.50	3.606%	$67.8619	$67.86	$67.85	$67.90
Purchase #7	$43.77	13.688%	$49.7612	$49.76	$49.75	$49.80
7 purchase totals =	$972.35		$1,076.6503	$1,076.65	$1,076.60	$1,076.80