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	$74.58	10.836%	$82.6615	$82.66	$82.65	$82.70
Purchase #2	$57.39	7.272%	$61.5634	$61.56	$61.55	$61.60
Purchase #3	$153.89	7.132%	$164.8654	$164.87	$164.85	$164.90
Purchase #4	$111.31	6.519%	$118.5663	$118.57	$118.55	$118.60
Purchase #5	$178.96	10.286%	$197.3678	$197.37	$197.35	$197.40
Purchase #6	$240.82	3.466%	$249.1668	$249.17	$249.15	$249.20
Purchase #7	$192.25	11.452%	$214.2665	$214.27	$214.25	$214.30
7 purchase totals =	$1,009.20		$1,088.4577	$1,088.47	$1,088.35	$1,088.70