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	$74.83	13.779%	$85.1408	$85.14	$85.15	$85.10
Purchase #2	$168.29	9.643%	$184.5182	$184.52	$184.50	$184.50
Purchase #3	$14.48	7.159%	$15.5166	$15.52	$15.50	$15.50
Purchase #4	$26.38	6.564%	$28.1116	$28.11	$28.10	$28.10
Purchase #5	$247.95	4.280%	$258.5623	$258.56	$258.55	$258.60
Purchase #6	$162.69	10.622%	$179.9709	$179.97	$179.95	$180.00
Purchase #7	$149.46	4.703%	$156.4891	$156.49	$156.50	$156.50
7 purchase totals =	$844.08		$908.3095	$908.31	$908.25	$908.30