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	$181.31	10.429%	$200.2188	$200.22	$200.20	$200.20
Purchase #2	$143.84	6.839%	$153.6772	$153.68	$153.70	$153.70
Purchase #3	$18.25	12.773%	$20.5811	$20.58	$20.60	$20.60
Purchase #4	$88.37	5.152%	$92.9228	$92.92	$92.90	$92.90
Purchase #5	$42.98	10.571%	$47.5234	$47.52	$47.50	$47.50
Purchase #6	$229.69	3.350%	$237.3846	$237.38	$237.40	$237.40
Purchase #7	$19.57	10.107%	$21.5479	$21.55	$21.55	$21.50
7 purchase totals =	$724.01		$773.8558	$773.85	$773.85	$773.80