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	$85.60	13.236%	$96.93	$96.93	$96.95	$96.90
Purchase #2	$67.63	5.550%	$71.3835	$71.38	$71.40	$71.40
Purchase #3	$137.31	6.784%	$146.6251	$146.63	$146.65	$146.60
Purchase #4	$152.45	9.492%	$166.9206	$166.92	$166.90	$166.90
Purchase #5	$134.65	5.782%	$142.4355	$142.44	$142.45	$142.40
Purchase #6	$19.50	8.147%	$21.0887	$21.09	$21.10	$21.10
Purchase #7	$227.75	3.615%	$235.9832	$235.98	$236.00	$236.00
7 purchase totals =	$824.89		$881.3666	$881.37	$881.45	$881.30