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	$155.54	5.715%	$164.4291	$164.43	$164.45	$164.40
Purchase #2	$115.45	4.590%	$120.7492	$120.75	$120.75	$120.70
Purchase #3	$165.57	12.773%	$186.7183	$186.72	$186.70	$186.70
Purchase #4	$175.50	11.807%	$196.2213	$196.22	$196.20	$196.20
Purchase #5	$19.58	11.822%	$21.8947	$21.89	$21.90	$21.90
Purchase #6	$235.27	5.665%	$248.598	$248.60	$248.60	$248.60
Purchase #7	$108.96	8.284%	$117.9862	$117.99	$118.00	$118.00
7 purchase totals =	$975.87		$1,056.5968	$1,056.60	$1,056.60	$1,056.50