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	$158.75	5.784%	$167.9321	$167.93	$167.95	$167.90
Purchase #2	$48.87	12.222%	$54.8429	$54.84	$54.85	$54.80
Purchase #3	$192.31	11.762%	$214.9295	$214.93	$214.95	$214.90
Purchase #4	$171.84	6.357%	$182.7639	$182.76	$182.75	$182.80
Purchase #5	$105.29	5.592%	$111.1778	$111.18	$111.20	$111.20
Purchase #6	$140.63	5.407%	$148.2339	$148.23	$148.25	$148.20
Purchase #7	$67.40	8.248%	$72.9592	$72.96	$72.95	$73.00
7 purchase totals =	$885.09		$952.8393	$952.83	$952.90	$952.80