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	$54.61	9.248%	$59.6603	$59.66	$59.65	$59.70
Purchase #2	$84.98	8.296%	$92.0299	$92.03	$92.05	$92.00
Purchase #3	$239.46	7.293%	$256.9238	$256.92	$256.90	$256.90
Purchase #4	$55.35	11.816%	$61.8902	$61.89	$61.90	$61.90
Purchase #5	$106.53	10.866%	$118.1055	$118.11	$118.10	$118.10
Purchase #6	$13.71	3.444%	$14.1822	$14.18	$14.20	$14.20
Purchase #7	$165.86	13.108%	$187.6009	$187.60	$187.60	$187.60
7 purchase totals =	$720.50		$790.3928	$790.39	$790.40	$790.40