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	$90.51	4.384%	$94.478	$94.48	$94.50	$94.50
Purchase #2	$241.40	3.813%	$250.6046	$250.60	$250.60	$250.60
Purchase #3	$192.63	11.500%	$214.7825	$214.78	$214.80	$214.80
Purchase #4	$233.56	9.272%	$255.2157	$255.22	$255.20	$255.20
Purchase #5	$27.70	13.553%	$31.4542	$31.45	$31.45	$31.50
Purchase #6	$139.74	13.208%	$158.1969	$158.20	$158.20	$158.20
Purchase #7	$168.96	4.125%	$175.9296	$175.93	$175.95	$175.90
7 purchase totals =	$1,094.50		$1,180.6615	$1,180.66	$1,180.70	$1,180.70