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	$89.25	5.596%	$94.2444	$94.24	$94.25	$94.20
Purchase #2	$109.34	13.190%	$123.7619	$123.76	$123.75	$123.80
Purchase #3	$167.73	9.204%	$183.1679	$183.17	$183.15	$183.20
Purchase #4	$180.26	3.784%	$187.081	$187.08	$187.10	$187.10
Purchase #5	$43.32	12.693%	$48.8186	$48.82	$48.80	$48.80
Purchase #6	$62.64	4.698%	$65.5828	$65.58	$65.60	$65.60
Purchase #7	$93.56	5.472%	$98.6796	$98.68	$98.70	$98.70
7 purchase totals =	$746.10		$801.3362	$801.33	$801.35	$801.40