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	$105.40	11.185%	$117.189	$117.19	$117.20	$117.20
Purchase #2	$38.96	10.168%	$42.9215	$42.92	$42.90	$42.90
Purchase #3	$56.66	10.622%	$62.6784	$62.68	$62.70	$62.70
Purchase #4	$48.81	7.487%	$52.4644	$52.46	$52.45	$52.50
Purchase #5	$92.56	6.514%	$98.5894	$98.59	$98.60	$98.60
Purchase #6	$41.76	4.575%	$43.6705	$43.67	$43.65	$43.70
Purchase #7	$142.43	6.754%	$152.0497	$152.05	$152.05	$152.00
7 purchase totals =	$526.58		$569.5629	$569.56	$569.55	$569.60