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	$122.85	7.575%	$132.1559	$132.16	$132.15	$132.20
Purchase #2	$145.55	12.843%	$164.243	$164.24	$164.25	$164.20
Purchase #3	$103.86	7.409%	$111.555	$111.56	$111.55	$111.60
Purchase #4	$219.52	6.403%	$233.5759	$233.58	$233.60	$233.60
Purchase #5	$238.76	8.234%	$258.4195	$258.42	$258.40	$258.40
Purchase #6	$60.34	4.641%	$63.1404	$63.14	$63.15	$63.10
Purchase #7	$113.94	10.372%	$125.7579	$125.76	$125.75	$125.80
7 purchase totals =	$1,004.82		$1,088.8476	$1,088.86	$1,088.85	$1,088.90