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	$154.37	8.324%	$167.2198	$167.22	$167.20	$167.20
Purchase #2	$173.74	13.112%	$196.5208	$196.52	$196.50	$196.50
Purchase #3	$47.40	7.555%	$50.9811	$50.98	$51.00	$51.00
Purchase #4	$38.28	9.866%	$42.0567	$42.06	$42.05	$42.10
Purchase #5	$138.34	5.855%	$146.4398	$146.44	$146.45	$146.40
Purchase #6	$160.84	7.155%	$172.3481	$172.35	$172.35	$172.30
Purchase #7	$187.32	3.125%	$193.1738	$193.17	$193.15	$193.20
7 purchase totals =	$900.29		$968.7401	$968.74	$968.70	$968.70