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	$241.51	3.767%	$250.6077	$250.61	$250.60	$250.60
Purchase #2	$233.76	13.526%	$265.3784	$265.38	$265.40	$265.40
Purchase #3	$78.31	3.283%	$80.8809	$80.88	$80.90	$80.90
Purchase #4	$116.67	9.226%	$127.434	$127.43	$127.45	$127.40
Purchase #5	$92.25	8.156%	$99.7739	$99.77	$99.75	$99.80
Purchase #6	$218.74	3.153%	$225.6369	$225.64	$225.65	$225.60
Purchase #7	$19.83	7.830%	$21.3827	$21.38	$21.40	$21.40
7 purchase totals =	$1,001.07		$1,071.0945	$1,071.09	$1,071.15	$1,071.10