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	$41.41	4.355%	$43.2134	$43.21	$43.20	$43.20
Purchase #2	$46.27	10.356%	$51.0617	$51.06	$51.05	$51.10
Purchase #3	$32.74	3.689%	$33.9478	$33.95	$33.95	$33.90
Purchase #4	$230.52	11.461%	$256.9399	$256.94	$256.95	$256.90
Purchase #5	$31.58	10.262%	$34.8207	$34.82	$34.80	$34.80
Purchase #6	$69.92	3.369%	$72.2756	$72.28	$72.30	$72.30
Purchase #7	$87.74	13.194%	$99.3164	$99.32	$99.30	$99.30
7 purchase totals =	$540.18		$591.5755	$591.58	$591.55	$591.50