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	$82.94	7.702%	$89.328	$89.33	$89.35	$89.30
Purchase #2	$187.61	8.432%	$203.4293	$203.43	$203.45	$203.40
Purchase #3	$186.30	6.245%	$197.9344	$197.93	$197.95	$197.90
Purchase #4	$138.70	8.845%	$150.968	$150.97	$150.95	$151.00
Purchase #5	$92.25	7.867%	$99.5073	$99.51	$99.50	$99.50
Purchase #6	$224.43	6.153%	$238.2392	$238.24	$238.25	$238.20
Purchase #7	$150.93	8.663%	$164.0051	$164.01	$164.00	$164.00
7 purchase totals =	$1,063.16		$1,143.4113	$1,143.42	$1,143.45	$1,143.30