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	$221.80	7.758%	$239.0072	$239.01	$239.00	$239.00
Purchase #2	$118.29	7.793%	$127.5083	$127.51	$127.50	$127.50
Purchase #3	$109.43	3.565%	$113.3312	$113.33	$113.35	$113.30
Purchase #4	$9.28	8.723%	$10.0895	$10.09	$10.10	$10.10
Purchase #5	$88.59	6.627%	$94.4609	$94.46	$94.45	$94.50
Purchase #6	$142.40	12.475%	$160.1644	$160.16	$160.15	$160.20
Purchase #7	$247.41	3.384%	$255.7824	$255.78	$255.80	$255.80
7 purchase totals =	$937.20		$1,000.3439	$1,000.34	$1,000.35	$1,000.40