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	$207.58	3.229%	$214.2828	$214.28	$214.30	$214.30
Purchase #2	$152.90	6.330%	$162.5786	$162.58	$162.60	$162.60
Purchase #3	$99.33	4.603%	$103.9022	$103.90	$103.90	$103.90
Purchase #4	$64.44	8.827%	$70.1281	$70.13	$70.15	$70.10
Purchase #5	$220.30	3.193%	$227.3342	$227.33	$227.35	$227.30
Purchase #6	$17.93	13.256%	$20.3068	$20.31	$20.30	$20.30
Purchase #7	$94.64	11.445%	$105.4715	$105.47	$105.45	$105.50
7 purchase totals =	$857.12		$904.0042	$904.00	$904.05	$904.00