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	$41.70	5.184%	$43.8617	$43.86	$43.85	$43.90
Purchase #2	$162.59	9.802%	$178.5271	$178.53	$178.55	$178.50
Purchase #3	$70.39	11.185%	$78.2631	$78.26	$78.25	$78.30
Purchase #4	$114.44	11.428%	$127.5182	$127.52	$127.50	$127.50
Purchase #5	$145.69	12.667%	$164.1446	$164.14	$164.15	$164.10
Purchase #6	$160.45	8.135%	$173.5026	$173.50	$173.50	$173.50
Purchase #7	$191.36	7.194%	$205.1264	$205.13	$205.15	$205.10
7 purchase totals =	$886.62		$970.9437	$970.94	$970.95	$970.90