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	$144.56	13.861%	$164.5975	$164.60	$164.60	$164.60
Purchase #2	$138.46	12.280%	$155.4629	$155.46	$155.45	$155.50
Purchase #3	$99.50	3.462%	$102.9447	$102.94	$102.95	$102.90
Purchase #4	$14.94	9.274%	$16.3255	$16.33	$16.35	$16.30
Purchase #5	$97.56	7.731%	$105.1024	$105.10	$105.10	$105.10
Purchase #6	$126.47	11.294%	$140.7535	$140.75	$140.75	$140.80
Purchase #7	$198.53	8.392%	$215.1906	$215.19	$215.20	$215.20
7 purchase totals =	$820.02		$900.3771	$900.37	$900.40	$900.40