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	$60.49	10.517%	$66.8517	$66.85	$66.85	$66.90
Purchase #2	$47.45	6.659%	$50.6097	$50.61	$50.60	$50.60
Purchase #3	$220.33	11.342%	$245.3198	$245.32	$245.30	$245.30
Purchase #4	$11.28	11.317%	$12.5566	$12.56	$12.55	$12.60
Purchase #5	$101.61	12.558%	$114.3702	$114.37	$114.35	$114.40
Purchase #6	$175.63	5.256%	$184.8611	$184.86	$184.85	$184.90
Purchase #7	$50.47	8.719%	$54.8705	$54.87	$54.85	$54.90
7 purchase totals =	$667.26		$729.4396	$729.44	$729.35	$729.60