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	$135.36	7.771%	$145.8788	$145.88	$145.90	$145.90
Purchase #2	$42.37	7.576%	$45.58	$45.58	$45.60	$45.60
Purchase #3	$176.85	11.193%	$196.6448	$196.64	$196.65	$196.60
Purchase #4	$90.65	13.791%	$103.1515	$103.15	$103.15	$103.20
Purchase #5	$134.31	8.232%	$145.3664	$145.37	$145.35	$145.40
Purchase #6	$25.48	9.212%	$27.8272	$27.83	$27.85	$27.80
Purchase #7	$172.42	4.187%	$179.6392	$179.64	$179.65	$179.60
7 purchase totals =	$777.44		$844.0879	$844.09	$844.15	$844.10