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	$77.83	6.750%	$83.0835	$83.08	$83.10	$83.10
Purchase #2	$182.71	4.110%	$190.2194	$190.22	$190.20	$190.20
Purchase #3	$238.80	7.324%	$256.2897	$256.29	$256.30	$256.30
Purchase #4	$176.75	4.114%	$184.0215	$184.02	$184.00	$184.00
Purchase #5	$132.66	4.342%	$138.4201	$138.42	$138.40	$138.40
Purchase #6	$111.81	7.444%	$120.1331	$120.13	$120.15	$120.10
Purchase #7	$89.87	10.354%	$99.1751	$99.18	$99.20	$99.20
7 purchase totals =	$1,010.43		$1,071.3424	$1,071.34	$1,071.35	$1,071.30