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	$106.85	5.601%	$112.8347	$112.83	$112.85	$112.80
Purchase #2	$217.33	7.598%	$233.8427	$233.84	$233.85	$233.80
Purchase #3	$204.88	10.111%	$225.5954	$225.60	$225.60	$225.60
Purchase #4	$169.45	12.146%	$190.0314	$190.03	$190.05	$190.00
Purchase #5	$142.80	9.354%	$156.1575	$156.16	$156.15	$156.20
Purchase #6	$121.60	7.433%	$130.6385	$130.64	$130.65	$130.60
Purchase #7	$41.76	7.823%	$45.0269	$45.03	$45.05	$45.00
7 purchase totals =	$1,004.67		$1,094.1271	$1,094.13	$1,094.20	$1,094.00