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	$110.92	7.156%	$118.8574	$118.86	$118.85	$118.90
Purchase #2	$227.29	12.229%	$255.0853	$255.09	$255.10	$255.10
Purchase #3	$78.98	6.308%	$83.9621	$83.96	$83.95	$84.00
Purchase #4	$158.86	9.132%	$173.3671	$173.37	$173.35	$173.40
Purchase #5	$194.61	6.239%	$206.7517	$206.75	$206.75	$206.80
Purchase #6	$159.33	5.362%	$167.8733	$167.87	$167.85	$167.90
Purchase #7	$12.44	7.339%	$13.353	$13.35	$13.35	$13.40
7 purchase totals =	$942.43		$1,019.2499	$1,019.25	$1,019.20	$1,019.50