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	$245.89	4.352%	$256.5911	$256.59	$256.60	$256.60
Purchase #2	$134.91	6.466%	$143.6333	$143.63	$143.65	$143.60
Purchase #3	$244.64	10.522%	$270.381	$270.38	$270.40	$270.40
Purchase #4	$233.83	10.270%	$257.8443	$257.84	$257.85	$257.80
Purchase #5	$88.69	9.227%	$96.8734	$96.87	$96.85	$96.90
Purchase #6	$147.68	13.312%	$167.3392	$167.34	$167.35	$167.30
Purchase #7	$15.37	3.375%	$15.8887	$15.89	$15.90	$15.90
7 purchase totals =	$1,111.01		$1,208.5510	$1,208.54	$1,208.60	$1,208.50