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	$208.51	8.756%	$226.7671	$226.77	$226.75	$226.80
Purchase #2	$101.76	3.474%	$105.2951	$105.30	$105.30	$105.30
Purchase #3	$111.63	4.163%	$116.2772	$116.28	$116.30	$116.30
Purchase #4	$115.47	13.842%	$131.4534	$131.45	$131.45	$131.50
Purchase #5	$56.53	3.455%	$58.4831	$58.48	$58.50	$58.50
Purchase #6	$24.94	9.810%	$27.3866	$27.39	$27.40	$27.40
Purchase #7	$82.61	10.109%	$90.961	$90.96	$90.95	$91.00
7 purchase totals =	$701.45		$756.6235	$756.63	$756.65	$756.80