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	$97.55	13.835%	$111.046	$111.05	$111.05	$111.00
Purchase #2	$171.50	9.355%	$187.5438	$187.54	$187.55	$187.50
Purchase #3	$120.84	5.575%	$127.5768	$127.58	$127.60	$127.60
Purchase #4	$31.68	9.753%	$34.7698	$34.77	$34.75	$34.80
Purchase #5	$164.30	5.312%	$173.0276	$173.03	$173.05	$173.00
Purchase #6	$119.36	10.650%	$132.0718	$132.07	$132.05	$132.10
Purchase #7	$211.69	13.529%	$240.3295	$240.33	$240.35	$240.30
7 purchase totals =	$916.92		$1,006.3653	$1,006.37	$1,006.40	$1,006.30