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	$95.42	5.780%	$100.9353	$100.94	$100.95	$100.90
Purchase #2	$64.62	12.851%	$72.9243	$72.92	$72.90	$72.90
Purchase #3	$155.87	11.855%	$174.3484	$174.35	$174.35	$174.30
Purchase #4	$160.74	13.243%	$182.0268	$182.03	$182.05	$182.00
Purchase #5	$103.86	5.115%	$109.1724	$109.17	$109.15	$109.20
Purchase #6	$214.58	6.418%	$228.3517	$228.35	$228.35	$228.40
Purchase #7	$35.93	9.861%	$39.4731	$39.47	$39.45	$39.50
7 purchase totals =	$831.02		$907.2320	$907.23	$907.20	$907.20