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	$30.87	8.687%	$33.5517	$33.55	$33.55	$33.60
Purchase #2	$206.25	9.590%	$226.0294	$226.03	$226.05	$226.00
Purchase #3	$180.56	13.812%	$205.4989	$205.50	$205.50	$205.50
Purchase #4	$70.55	9.283%	$77.0992	$77.10	$77.10	$77.10
Purchase #5	$186.28	7.542%	$200.3292	$200.33	$200.35	$200.30
Purchase #6	$249.55	5.158%	$262.4218	$262.42	$262.40	$262.40
Purchase #7	$107.66	3.532%	$111.4626	$111.46	$111.45	$111.50
7 purchase totals =	$1,031.72		$1,116.3928	$1,116.39	$1,116.40	$1,116.40