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	$80.35	11.840%	$89.8634	$89.86	$89.85	$89.90
Purchase #2	$192.32	8.418%	$208.5095	$208.51	$208.50	$208.50
Purchase #3	$152.84	4.857%	$160.2634	$160.26	$160.25	$160.30
Purchase #4	$54.66	13.326%	$61.944	$61.94	$61.95	$61.90
Purchase #5	$8.78	7.409%	$9.4305	$9.43	$9.45	$9.40
Purchase #6	$9.69	9.396%	$10.6005	$10.60	$10.60	$10.60
Purchase #7	$68.83	4.380%	$71.8448	$71.84	$71.85	$71.80
7 purchase totals =	$567.47		$612.4561	$612.44	$612.45	$612.40