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	$138.35	9.492%	$151.4822	$151.48	$151.50	$151.50
Purchase #2	$176.93	7.634%	$190.4368	$190.44	$190.45	$190.40
Purchase #3	$92.43	10.230%	$101.8856	$101.89	$101.90	$101.90
Purchase #4	$232.50	10.612%	$257.1729	$257.17	$257.15	$257.20
Purchase #5	$84.57	5.259%	$89.0175	$89.02	$89.00	$89.00
Purchase #6	$250.68	9.680%	$274.9458	$274.95	$274.95	$274.90
Purchase #7	$10.49	4.373%	$10.9487	$10.95	$10.95	$10.90
7 purchase totals =	$985.95		$1,075.8895	$1,075.90	$1,075.90	$1,075.80