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	$148.89	10.573%	$164.6321	$164.63	$164.65	$164.60
Purchase #2	$155.76	11.166%	$173.1522	$173.15	$173.15	$173.20
Purchase #3	$40.83	5.800%	$43.1981	$43.20	$43.20	$43.20
Purchase #4	$57.77	11.617%	$64.4811	$64.48	$64.50	$64.50
Purchase #5	$221.78	11.603%	$247.5131	$247.51	$247.50	$247.50
Purchase #6	$178.67	7.699%	$192.4258	$192.43	$192.45	$192.40
Purchase #7	$108.67	10.604%	$120.1934	$120.19	$120.20	$120.20
7 purchase totals =	$912.37		$1,005.5958	$1,005.59	$1,005.65	$1,005.60