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	$181.78	5.142%	$191.1271	$191.13	$191.15	$191.10
Purchase #2	$181.77	9.294%	$198.6637	$198.66	$198.65	$198.70
Purchase #3	$27.68	13.390%	$31.3864	$31.39	$31.40	$31.40
Purchase #4	$107.78	11.617%	$120.3008	$120.30	$120.30	$120.30
Purchase #5	$145.79	11.296%	$162.2584	$162.26	$162.25	$162.30
Purchase #6	$234.60	11.647%	$261.9239	$261.92	$261.90	$261.90
Purchase #7	$12.29	6.295%	$13.0637	$13.06	$13.05	$13.10
7 purchase totals =	$891.69		$978.7240	$978.72	$978.70	$978.80