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	$165.64	11.162%	$184.1287	$184.13	$184.15	$184.10
Purchase #2	$217.32	3.690%	$225.3391	$225.34	$225.35	$225.30
Purchase #3	$205.25	4.460%	$214.4042	$214.40	$214.40	$214.40
Purchase #4	$205.50	13.781%	$233.82	$233.82	$233.80	$233.80
Purchase #5	$65.86	8.435%	$71.4153	$71.42	$71.40	$71.40
Purchase #6	$34.36	12.378%	$38.6131	$38.61	$38.60	$38.60
Purchase #7	$189.46	4.582%	$198.1411	$198.14	$198.15	$198.10
7 purchase totals =	$1,083.39		$1,165.8615	$1,165.86	$1,165.85	$1,165.70