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	$158.28	4.149%	$164.847	$164.85	$164.85	$164.80
Purchase #2	$130.25	9.452%	$142.5612	$142.56	$142.55	$142.60
Purchase #3	$189.58	3.629%	$196.4599	$196.46	$196.45	$196.50
Purchase #4	$63.71	12.249%	$71.5138	$71.51	$71.50	$71.50
Purchase #5	$85.61	8.741%	$93.0932	$93.09	$93.10	$93.10
Purchase #6	$181.87	7.835%	$196.1195	$196.12	$196.10	$196.10
Purchase #7	$31.69	11.268%	$35.2608	$35.26	$35.25	$35.30
7 purchase totals =	$840.99		$899.8554	$899.85	$899.80	$899.90