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	$136.50	5.666%	$144.2341	$144.23	$144.25	$144.20
Purchase #2	$250.77	13.573%	$284.807	$284.81	$284.80	$284.80
Purchase #3	$41.39	9.781%	$45.4384	$45.44	$45.45	$45.40
Purchase #4	$200.91	6.690%	$214.3509	$214.35	$214.35	$214.40
Purchase #5	$62.58	11.564%	$69.8168	$69.82	$69.80	$69.80
Purchase #6	$227.51	12.189%	$255.2412	$255.24	$255.25	$255.20
Purchase #7	$167.45	6.684%	$178.6424	$178.64	$178.65	$178.60
7 purchase totals =	$1,087.11		$1,192.5308	$1,192.53	$1,192.55	$1,192.40