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	$145.54	9.536%	$159.4187	$159.42	$159.40	$159.40
Purchase #2	$122.69	3.606%	$127.1142	$127.11	$127.10	$127.10
Purchase #3	$79.94	13.270%	$90.548	$90.55	$90.55	$90.50
Purchase #4	$208.53	12.120%	$233.8038	$233.80	$233.80	$233.80
Purchase #5	$105.28	5.396%	$110.9609	$110.96	$110.95	$111.00
Purchase #6	$151.96	5.290%	$159.9987	$160.00	$160.00	$160.00
Purchase #7	$153.32	6.154%	$162.7553	$162.76	$162.75	$162.80
7 purchase totals =	$967.26		$1,044.5996	$1,044.60	$1,044.55	$1,044.60