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	$105.87	7.392%	$113.6959	$113.70	$113.70	$113.70
Purchase #2	$143.75	5.743%	$152.0056	$152.01	$152.00	$152.00
Purchase #3	$80.40	11.747%	$89.8446	$89.84	$89.85	$89.80
Purchase #4	$33.92	12.704%	$38.2292	$38.23	$38.25	$38.20
Purchase #5	$193.39	11.143%	$214.9394	$214.94	$214.95	$214.90
Purchase #6	$176.26	13.750%	$200.4958	$200.50	$200.50	$200.50
Purchase #7	$54.64	11.860%	$61.1203	$61.12	$61.10	$61.10
7 purchase totals =	$788.23		$870.3308	$870.34	$870.35	$870.20