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	$123.33	3.607%	$127.7785	$127.78	$127.80	$127.80
Purchase #2	$112.65	10.371%	$124.3329	$124.33	$124.35	$124.30
Purchase #3	$100.45	5.274%	$105.7477	$105.75	$105.75	$105.70
Purchase #4	$249.37	10.186%	$274.7708	$274.77	$274.75	$274.80
Purchase #5	$11.70	3.360%	$12.0931	$12.09	$12.10	$12.10
Purchase #6	$31.57	9.121%	$34.4495	$34.45	$34.45	$34.40
Purchase #7	$49.41	5.870%	$52.3104	$52.31	$52.30	$52.30
7 purchase totals =	$678.48		$731.4829	$731.48	$731.50	$731.40