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	$34.57	11.258%	$38.4619	$38.46	$38.45	$38.50
Purchase #2	$66.56	3.755%	$69.0593	$69.06	$69.05	$69.10
Purchase #3	$30.45	13.109%	$34.4417	$34.44	$34.45	$34.40
Purchase #4	$84.95	6.454%	$90.4327	$90.43	$90.45	$90.40
Purchase #5	$12.86	10.521%	$14.213	$14.21	$14.20	$14.20
Purchase #6	$47.42	7.413%	$50.9352	$50.94	$50.95	$50.90
Purchase #7	$63.90	5.449%	$67.3819	$67.38	$67.40	$67.40
7 purchase totals =	$340.71		$364.9257	$364.92	$364.95	$364.90