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	$157.43	5.577%	$166.2099	$166.21	$166.20	$166.20
Purchase #2	$130.51	6.845%	$139.4434	$139.44	$139.45	$139.40
Purchase #3	$135.68	5.149%	$142.6662	$142.67	$142.65	$142.70
Purchase #4	$126.49	4.126%	$131.709	$131.71	$131.70	$131.70
Purchase #5	$179.61	9.389%	$196.4736	$196.47	$196.45	$196.50
Purchase #6	$159.40	3.543%	$165.0475	$165.05	$165.05	$165.00
Purchase #7	$200.61	11.249%	$223.1766	$223.18	$223.20	$223.20
7 purchase totals =	$1,089.73		$1,164.7262	$1,164.73	$1,164.70	$1,164.70