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	$149.59	5.827%	$158.3066	$158.31	$158.30	$158.30
Purchase #2	$58.52	12.851%	$66.0404	$66.04	$66.05	$66.00
Purchase #3	$113.25	8.823%	$123.242	$123.24	$123.25	$123.20
Purchase #4	$9.57	5.537%	$10.0999	$10.10	$10.10	$10.10
Purchase #5	$177.63	5.312%	$187.0657	$187.07	$187.05	$187.10
Purchase #6	$37.33	12.565%	$42.0205	$42.02	$42.00	$42.00
Purchase #7	$118.84	7.547%	$127.8089	$127.81	$127.80	$127.80
7 purchase totals =	$664.73		$714.5840	$714.59	$714.55	$714.50