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	$86.51	5.109%	$90.9298	$90.93	$90.95	$90.90
Purchase #2	$237.39	13.183%	$268.6851	$268.69	$268.70	$268.70
Purchase #3	$38.39	5.319%	$40.432	$40.43	$40.45	$40.40
Purchase #4	$114.49	11.113%	$127.2133	$127.21	$127.20	$127.20
Purchase #5	$82.83	5.739%	$87.5836	$87.58	$87.60	$87.60
Purchase #6	$94.27	10.433%	$104.1052	$104.11	$104.10	$104.10
Purchase #7	$22.59	3.536%	$23.3888	$23.39	$23.40	$23.40
7 purchase totals =	$676.47		$742.3378	$742.34	$742.40	$742.30