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	$88.69	9.796%	$97.3781	$97.38	$97.40	$97.40
Purchase #2	$69.29	5.160%	$72.8654	$72.87	$72.85	$72.90
Purchase #3	$67.94	6.476%	$72.3398	$72.34	$72.35	$72.30
Purchase #4	$17.42	6.350%	$18.5262	$18.53	$18.55	$18.50
Purchase #5	$54.55	12.228%	$61.2204	$61.22	$61.20	$61.20
Purchase #6	$17.27	7.202%	$18.5138	$18.51	$18.50	$18.50
Purchase #7	$173.67	10.809%	$192.442	$192.44	$192.45	$192.40
7 purchase totals =	$488.83		$533.2857	$533.29	$533.30	$533.20