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	$42.69	6.477%	$45.455	$45.46	$45.45	$45.50
Purchase #2	$217.51	10.834%	$241.075	$241.08	$241.10	$241.10
Purchase #3	$9.55	11.667%	$10.6642	$10.66	$10.65	$10.70
Purchase #4	$105.76	6.284%	$112.406	$112.41	$112.40	$112.40
Purchase #5	$178.32	10.395%	$196.8564	$196.86	$196.85	$196.90
Purchase #6	$116.89	10.493%	$129.1553	$129.16	$129.15	$129.20
Purchase #7	$64.48	5.777%	$68.205	$68.21	$68.20	$68.20
7 purchase totals =	$735.20		$803.8169	$803.84	$803.80	$804.00