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	$224.54	10.264%	$247.5868	$247.59	$247.60	$247.60
Purchase #2	$30.54	10.866%	$33.8585	$33.86	$33.85	$33.90
Purchase #3	$134.37	5.207%	$141.3666	$141.37	$141.35	$141.40
Purchase #4	$138.63	5.259%	$145.9206	$145.92	$145.90	$145.90
Purchase #5	$18.56	3.328%	$19.1777	$19.18	$19.20	$19.20
Purchase #6	$196.69	4.310%	$205.1673	$205.17	$205.15	$205.20
Purchase #7	$111.45	6.363%	$118.5416	$118.54	$118.55	$118.50
7 purchase totals =	$854.78		$911.6191	$911.63	$911.60	$911.70