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	$60.56	8.252%	$65.5574	$65.56	$65.55	$65.60
Purchase #2	$97.26	3.141%	$100.3149	$100.31	$100.30	$100.30
Purchase #3	$148.37	8.771%	$161.3835	$161.38	$161.40	$161.40
Purchase #4	$98.35	7.137%	$105.3692	$105.37	$105.35	$105.40
Purchase #5	$116.71	12.804%	$131.6535	$131.65	$131.65	$131.70
Purchase #6	$88.62	12.298%	$99.5185	$99.52	$99.50	$99.50
Purchase #7	$227.43	4.149%	$236.8661	$236.87	$236.85	$236.90
7 purchase totals =	$837.30		$900.6631	$900.66	$900.60	$900.80