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	$108.63	8.260%	$117.6028	$117.60	$117.60	$117.60
Purchase #2	$170.27	5.162%	$179.0593	$179.06	$179.05	$179.10
Purchase #3	$208.52	11.375%	$232.2392	$232.24	$232.25	$232.20
Purchase #4	$50.85	4.102%	$52.9359	$52.94	$52.95	$52.90
Purchase #5	$126.30	4.446%	$131.9153	$131.92	$131.90	$131.90
Purchase #6	$131.55	12.716%	$148.2779	$148.28	$148.30	$148.30
Purchase #7	$227.83	12.484%	$256.2723	$256.27	$256.25	$256.30
7 purchase totals =	$1,023.95		$1,118.3027	$1,118.31	$1,118.30	$1,118.30