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	$106.77	4.362%	$111.4273	$111.43	$111.45	$111.40
Purchase #2	$89.78	6.743%	$95.8339	$95.83	$95.85	$95.80
Purchase #3	$154.85	9.384%	$169.3811	$169.38	$169.40	$169.40
Purchase #4	$126.25	9.431%	$138.1566	$138.16	$138.15	$138.20
Purchase #5	$197.29	10.153%	$217.3209	$217.32	$217.30	$217.30
Purchase #6	$11.84	5.392%	$12.4784	$12.48	$12.50	$12.50
Purchase #7	$164.54	10.183%	$181.2951	$181.30	$181.30	$181.30
7 purchase totals =	$851.32		$925.8933	$925.90	$925.95	$925.90